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The Slime Molds: Myxomycetes a problem associated with organic mulch
Curtis E. Swift, Ph.D.
Colorado State University Extension,
Tri River Area
Summer is a time of beauty with flower gardens exhibiting all shades of color and texture. Even the various bark mulches used to shade the soil and retain moisture add greatly to this beauty. Redwood bark, reddish brown when first scattered over the ground, turns a brownish gray. Aspen bark, while gray when applied, turns black as it ages.
Occasionally during the summer gardeners notice a growth on their bark mulch which closely resembles - should I say it - Dog Vomit. Yes, our office even has had gardeners call after taking their dogs to the vet because their dogs `must have eaten something bad' causing them to get sick. Other gardeners blame this problem on a neighbor because `they don't keep their dogs in at night'. I've always been curious to know how many veterinarians prescribe medication to correct this condition and how many neighborhood problems have escalated due to `sick' dogs. Gardeners calling our office in an attempt to discover what type of plants could be causing their dog's stomach problem are often surprised when told this colorful, vomit-looking mass is a unique and fascinating organism.
Known as slime mold, they were once considered to be animals due to their creeping phase. DeBary, one of the founders of mycology, called them Mycetozoa, from the Greek words myketes (fungi), and zoon (animals). With DeBary's first use of Mycetozoa in 1887, the name continued to be used until the 1970's. Some previous researchers classified the slime molds in the phylum Protozoa of the animal kingdom.
Mycologists (those who study fungi) previously considered these strange organisms to belong to a class called Myxomycetes; myxa (slime) and myketes (fungi). Myxomycetes was the name first used by Macbride in his 1899 monograph of the slime molds. The use of the word was based on work done in 1833 by Link who considered these organisms as fungi. In Whitakers 'Five Kingdom' system Slime Molds are not in the Kingdom Fungi but are placed in the Protoctistans. See http://www.uoguelph.ca/~gbarron/Myxos/myxappen.htm for more information.
The slime molds live in cool, shady, moist places on decaying wood, leaves or other organic matter retaining abundant moisture. Bark mulch in a flower garden or shrub bed certainly fits that description. The same type of organism is often seen in the woods on decaying logs. Over 700 species are reported as existing.
Slime molds feed on decaying organic matter, bacteria, protozoa, and other minute organism which it engulfs and digests. In rare instances the slime molds have been known to creep over ornamentals, causing suffocation.
Life Cycle - A Simplified Version:
The vegetative body of the slime mold is a plasmodium, an amoeboid mass of protoplasm which has many nuclei and no definite cell wall. Under Western Colorado conditions, the creeping phase the common bark-inhabiting slime molds dries into hardened structures producing dark masses of spore-like bodies and clouds of dust-like particles when body breaks apart. Some slime molds are known to move into drier, more exposed locations in order to accomplish this life cycle change.
The spores, capable of surviving unfavorable weather, are spread by wind, water, mowers, or other equipment. Under cool, humid conditions, the spores absorb water, crack open and release a single motile spore. Each motile (swarm) spore feeds like the plasmodium undergoing several changes before uniting with another spore to produce an amoeboid zygote. The zygote enlarges, becomes multinucleate and forms a plasmodium.
Some species produce a stalk of hardened cells which other cells climb to create a fruiting structure from which spores are produced. This starts the cycle over again.
For a more detailed discussion of slime molds and their life cycles, see the book by Stephenson and Stempen listed as a reference.
Slime Molds of Turf:
The colonies of slime mold living on logs and bark mulch can be strikingly colorful in yellow, orange or red. Some slime molds produce cream-colored masses of cells along grass blades. While most often found in moist climates, several of these grass-inhabiting slime molds are found in Western Colorado. Slime molds often appear in the same area of the lawn year after year in four to six inch patches in various shades of purple, gray, white or cream.
Preventive chemical treatments tried over the years have been found ineffective. Slime molds are more a curiosity or nuisance than a threat to gardens or lawns. Once a colony starts to form, allowing mulch to dry out, or using a garden or leaf rake in the affected area helps break up the colony and provides some control. Washing the grass down with a forceful stream of water breaks up colonies. Mowing also is an effective way to remove slime mold from turf. Like nature's other organisms, slime molds should be looked at for their beauty and enjoyed as one enjoys a mass planting of dianthus or snapdragons.
Agrios, G.N. 1988. Plant Pathology. Academic Press, Inc.
Alexopoulos, C.J. & Mims, C.W. 1979. Introductory Mycology: Third Edition. John Wiley & Sons.
Stephenson, S.L. & Stempen, H. 1994. Myxomycetes: A Handbook of Slime Molds. Timber Press, Portland, Oregon
Placed on the Internet July 4, 1997
Updated May 25, 2009 | <urn:uuid:357f2868-5ff7-470e-8a92-50234b8c91fb> | 2.8125 | 1,261 | Knowledge Article | Science & Tech. | 50.165356 |
Immunoglobulins (IG), T cell receptors (TR) and major histocompatibility (MH) appeared in the early jawed vertebrates about 450 millions years ago. These complex gene families are responsible of the specific (or adaptive) immune response in vertebrates.
The IMGT taxonomy tree describes the classification of the vertebrate species present in IMGT/LIGM-DB the largest IMGT database, and in the other IMGT databases, Web ressources and tools, according to the NCBI taxonomy (1).
All levels of classification shown in the trees (except the ones in dotted rectangles) can be
queried in the Taxonomy module of IMGT/LIGM-DB.
Most species English names can also be queried.
Click on yellow rectangles to see the IMGT taxonomy detailed trees.
IMGT taxonomy detailed trees
|Vertebrata||→ Chondrichthyes (cartilaginous fishes)|
|→ Actinopterygii (ray-finned fishes)||→ Euteleostei|
|→ Tetrapoda (tetrapods)||→ Eutheria (placentals)||→ Rodentia (rodents)|
Exceptionally, non-vertebrate sequences have been entered in IMGT-LIGM-DB. There are :
|(1)||For vertebrates with IG, TR and MH (that is jawed vertebrates or Gnathostomata):
Go to the "The taxonomy browser" page.
In "Query", tape "Vertebrata".
Start Search. Then click on "Gnathostomata". | <urn:uuid:3b1e3490-3f7a-4297-9413-47b1c8c7bf51> | 2.90625 | 354 | Structured Data | Science & Tech. | 25.844439 |
Optimize with a SATA RAID Storage Solution
Range of capacities as low as $1250 per TB. Ideal if you currently rely on servers/disks/JBODs
The Java platform's garbage collection mechanism greatly increases developer productivity, but a poorly implemented garbage collector can over-consume application resources. In this third article in the JVM performance optimization series, Eva Andreasson offers Java beginners an overview of the Java platform's memory model and GC mechanism. She then explains why fragmentation (and not GC) is the major "gotcha!" of Java application performance, and why generational garbage collection and compaction are currently the leading (though not most innovative) approaches to managing heap fragmentation in Java applications.
Garbage collection (GC) is the process that aims to free up occupied memory that is no longer referenced by any reachable Java object, and is an essential part of the Java virtual machine's (JVM's) dynamic memory management system. In a typical garbage collection cycle all objects that are still referenced, and thus reachable, are kept. The space occupied by previously referenced objects is freed and reclaimed to enable new object allocation.
In order to understand garbage collection and the various GC approaches and algorithms, you must first know a few things about the Java platform's memory model.
When you specify the startup option
-Xmx on the command line of your Java application (for instance:
java -Xmx:2g MyApp) memory is assigned to a Java process. This memory is referred to as the Java heap (or just heap). This is the dedicated memory address space where all objects created by your Java program (or sometimes the JVM) will be
allocated. As your Java program keeps running and allocating new objects, the Java heap (meaning that address space) will
Eventually, the Java heap will be full, which means that an allocating thread is unable to find a large-enough consecutive
section of free memory for the object it wants to allocate. At that point, the JVM determines that a garbage collection needs
to happen and it notifies the garbage collector. A garbage collection can also be triggered when a Java program calls
System.gc() does not guarantee a garbage collection. Before any garbage collection can start, a GC mechanism will first determine whether
it is safe to start it. It is safe to start a garbage collection when all of the application's active threads are at a safe
point to allow for it, e.g. simply explained it would be bad to start garbage collecting in the middle of an ongoing object
allocation, or in the middle of executing a sequence of optimized CPU instructions (see my previous article on compilers),
as you might lose context and thereby mess up end results.
A garbage collector should never reclaim an actively referenced object; to do so would break the Java virtual machine specification. A garbage collector is also not required to immediately collect dead objects. Dead objects are eventually collected during subsequent garbage collection cycles. While there are many ways to implement garbage collection, these two assumptions are true for all varieties. The real challenge of garbage collection is to identify everything that is live (still referenced) and reclaim any unreferenced memory, but do so without impacting running applications any more than necessary. A garbage collector thus has two mandates:
Earlier articles in the JVM performance optimization series:
Also on JavaWorld:
Books about garbage collection:
JVM tuning and GC algorithms: | <urn:uuid:138eb265-6f50-4387-957d-e3f707190983> | 3.25 | 705 | Truncated | Software Dev. | 29.511436 |
Marble Chips and Acids
Date: Around 1999
I would be ecstatic if you have, or know of any site
that does, an investigation on the reaction between hydrochloric acid and
marble chips. (I am investigating how the concentration of acid affects
It is for my GCSE coursework, and as i have missed the last 2/3 months of
school; due to serious health problems, i am desperately stuggling.
I would really appreciate it if you could help in all areas (plan,
conclusion and analysis etc.). If anyone has handed in or re-written a
GCSE investigation to do with this experiment, i would be SO grateful if
you would email me with either a web page or details.
Newton isn't in the business of doing people's schoolwork for them. We're
here to help them learn, which isn't the same thing.
You have chosen a somewhat difficult system to investigate, as it involves
two different phases (solid marble chips and liquid HCl in solution). The
progress of the reaction will depend on many variables other than the
concentration of the HCl. Two that are especially prominent because of the
two-phase nature are: 1. The ratio of surface area of the chips to the mass
of the chips. Smaller chips or chips of irregular shape will have
proportionately more surface area than large or blocky chips. 2. The
mixing between the two phases. As the reaction proceeds, HCl near the chips
will be depleted, and the concentration there will be less than the average
concentration throughout the reaction mixture. This could really throw off
your investigation. To minimize problem 1, you will need to use similar
marble chips for each experiment. They should be the same size and general
shape from run to run to give you interpretable results. For your analysis,
it may be a good idea to estimate the surface area (in, say, square
centimeters per gram) of the chips. This number may change as the reaction
proceeds, so you may also want to determine the area as a function of time
or extent of reaction as well. To minimize problem 2, you will need to keep
the reaction mixture well-mixed throughout the course of the reaction.
Before I go further, I should establish exactly what reaction is occurring.
CaCO3(s) + H+(aq) + Cl-(aq) --> Ca++(aq) + HCO3-(aq) + Cl-(aq)
HCO3-(aq) + H+(aq) + Cl-(aq) --> H2CO3(aq) + Cl-(aq)
H2CO3(aq) --> H2O + CO2(g)
Add these all together to get
CaCO3(s) + 2H+(aq) --> Ca++(aq) + H2O + CO2(g)
Depending on what the rate-determining step of this reaction is, the
kinetics should be either first or second order in acid.
There are several ways that you can follow the reaction, and it may be a
good idea to try more than one of them. As the reaction proceeds, solid
marble (CaCO3) disappears, acid (H+) is consumed, and carbon dioxide gas
(CO2) is produced. You could measure these by:
CaCO3: Stop the reaction after some period of time by filtering out and
washing the marble, and weigh it.
acid: Measure the pH of the reaction as it proceeds (requires a pH meter,
which is expensive), or fish out the marble and titrate the remaining acid.
CO2: Trap the gas evolved into an inverted graduated cylinder or a balloon,
and measure its volume. You could also trap it onto a chemical adsorbent,
such as Ascarite of soda lime, and weigh the charged sorbent. (Both
measurements would need to be corrected for water vapor in the collected
As for analysis and conclusions, you will need some data first. This should
be enough to get you started.
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
Click here to return to the Chemistry Archives
Update: June 2012 | <urn:uuid:bd492a79-a929-4761-867e-b392c6c14e7a> | 3.390625 | 904 | Knowledge Article | Science & Tech. | 59.013669 |
A habitable zone is the region around a star where an Earth-like planet can maintain liquid water on its surface. The habitable zone is the area that might potentially support life.
From the center of the earth to the far galaxies we find evidence that life arose from cosmic processes. The iron in our blood and the calcium in our bones were made inside stars. All silver and gold was forged by stars that exploded long ago.
The habitable zone first included the orbits of Venus to Mars, planets close enough to the sun for solar energy to make the chemistry of life, but not so close as to boil off water or break down the organic molecules on which life depends. The habitable zone may be larger than originally considered. The strong gravitational pull caused by large planets may produce enough energy to sufficiently heat the cores of orbiting moons. Life has proven itself tough here on Earth. It may be able to thrive in more extreme environments.
An imaginary spherical shell surrounding a star throughout which the surface temperatures of any planets present might be helpful to the origin and development of life as we know it. The single most crucial factor to the evolution of terrestrial life has been the ready availability of liquid water.
The "habitable zone" denotes the region around the star where we could in principle find liquid water, i.e. at a temperature between 0 and 100°C. It is also called the "Goldilocks Zone" (not too hot and not too cold). The figure shows the "habitable zone" in a star mass graph (in solar masses)./ semi-major axis (in astronomical units). Around more massive stars, the "habitable zone" is located in more distant regions. Copyright : Paris Observatory / UFE | <urn:uuid:bd2d7aac-4c4f-413e-8a78-949b237fd8f9> | 3.96875 | 347 | Knowledge Article | Science & Tech. | 44.841675 |
A sphere clearly already has a uniform geometric structure: its geometry looks the same no matter where you’re standing on the surface. A doughnut surface, by contrast, is anything but uniform: a region on the outer edge of the doughnut curves in a way that’s reminiscent of a sphere, while a region on the inner ring of the doughnut curves more like the surface of a saddle.
No matter how you try to place a torus in space — no matter how much stretching and distorting you do — there’s no way to make its geometry look the same at every point. Some parts will curve like a sphere and some like a saddle, and some parts may be flat.
Nevertheless, it’s possible to equip the torus with an abstract geometric structure that is identical at every point: simply declare that on each small patch of the torus, distances and angles are to be measured by taking the corresponding measurements on the square from which, as we’ve seen, the torus can be built. It’s impossible to build a physical torus inside ordinary space whose lengths and angles match this abstract rule, but this definition of lengths and angles is internally consistent. Since the square has ordinary flat (Euclidean) geometry, we say that the torus can be equipped with a Euclidean structure. A torus with this geometry is akin to a video game in which, when a creature exits the screen on the right, it reappears on the left, and when it exits at the top of the screen, it reappears at the bottom.
If we try to do the same thing for the double torus, however, we hit a snag. Recall that we can build a double torus by gluing the edges of an octagon. If we declare that geometry on the double torus shall mimic geometry on the octagon, we run into a problem at the octagon’s corners. After the octagon has been glued up into a double torus, the corner points are all glued together to form a single point on the double torus. Eight octagon corners meet up at that point, each corner contributing 135 degrees of angle measure, for a total of 1080 degrees, instead of the usual 360 degrees.
So if we try to give the double torus the same geometric structure as the octagon, we will end up with a double torus that has ordinary Euclidean geometry everywhere except at one point, where the surface buckles like a floppy hat with a sharp peak. (The corner points are not a problem when we glue a square to make a torus: we glue four 90-degree corners to get a perfect 360 degrees.)
To get a smooth geometric structure at the corner point on the double torus, we would need each of the octagon’s eight corners to contribute 45 degrees instead of 135 degrees. Remarkably, such an octagon does exist, but it lives not in the ordinary Euclidean plane but in another geometric structure called the hyperbolic disk: a third kind of geometry which is as uniform and internally consistent as spherical or Euclidean geometry, but which, because it is harder to visualize, was not even discovered by mathematicians until the early 19th century.
Roughly speaking, hyperbolic geometry is what you get if you declare that all the fish in Figure 3 are the same size. It’s as if Figure 3 is really the image of the hyperbolic disk through a distorted lens that makes the fish near the boundary look much smaller than the fish in the middle. In the real hyperbolic disk that is theoretically on the other side of the lens, the fish are all identical in size.
There’s no way to make a nice, smooth hyperbolic disk in ordinary space so that the fish truly are the same size. But once again, from an abstract point of view, the fish-sizing rule produces a geometry that is internally consistent and looks the same at every point — not when viewed by an outsider looking through the distorted lens, but from the perspective of someone who lives in the hyperbolic disk.
In hyperbolic geometry, the shortest path, or “geodesic,” between two points is the path that travels through the fewest possible fishes to get from one point to the other. Such a path, it turns out, is always a semicircle perpendicular to the boundary of the disk; the semicircles that go through the fishes’ spines are examples. From our distorted outside perspective, such paths look curved, but for an insider, these paths are the “straight lines”: to drive along one of them, you would never have to turn the steering wheel, as Thurston often put it. In contrast with the Euclidean plane, in which parallel lines always stay the same distance apart, in the hyperbolic disk, two lines that don’t intersect can spread apart from each other very quickly. | <urn:uuid:a844a1cd-44b3-4ddf-a4e1-7f6be528c845> | 3.65625 | 1,031 | Nonfiction Writing | Science & Tech. | 41.421724 |
May 15, 2009 | 44
If solar power is ever going to take off—and the world needs it to—photovoltaic cells will have to become a whole lot cheaper to produce.
Making solar cells from silicon, the most common approach, can be expensive and relatively inefficient at turning sunlight into electricity. As semiconductor manufacturer Applied Materials chief technology officer Mark Pinto told me last year: "With solar, it's all about cost."
But there are signs of improvement, writes Richard Swanson of SunPower Corp. in this week's Science. Last year, manufacturers made 5 gigawatts of photovoltaic panels. And some of these panels required just under six grams of silicon per watt of power—down from 15 grams at the turn of the century. And that watt of power now costs around $1.40 to produce compared with $2 or more in the 1990s.
May 13, 2009 | 5
Duke Energy wants to put a power plant on your house.
Over the next year, the utility plans to spend $50 million to plop a variety of photovoltaic panels on commercial buildings, the roofs of private homes, and other property in North Carolina.
Once installed, the 10 megawatts worth of solar panels are expected to produce enough alternating-current electricity to power 1,300 homes. But the utility’s main goals for the demonstration project are to gain experience with distributed generation—putting the power plant closer to the customer—and with integrating intermittent, renewable resources like sunshine into the grid.
Oct 8, 2008
Munich-based Phoenix Solar AG, a German photovoltaic system installer, has committed $615 million (450 million Euros) to purchasing Solyndra's cylindrical solar cells as a core part of its future rooftop installation business. Why? "We see significant cost-savings," says chief technology officer Manfred Bächler. "We simply do not need any supporting structures or ballasts or roof penetrations," because, unlike traditional flat solar panels, the new round kind don't need any help to keep grounded when the wind blows.
In addition, the ability of the solar cylinders to collect direct, diffuse and sunlight reflected from the rooftop—as well as the ability to lay panels of them horizontal to the roof itself means more electricity can be made from a given rooftop. Further, the solar cylinders keep cooler overall, which enhances the performance of the system, Bächler says.
Aug 15, 2008 | 4
The amount of solar photovoltaics harnessing electricity from sunshine in the U.S. will more than double by 2013, thanks to plans to build 800 megawatts (MW) worth in California. The two vast solar farms—covering more than 12 square miles—will be among the largest ever built in the world and dwarf the current U.S. record holder: Nellis Air Force Base in Nevada with 14 MW. In fact, the total amount of solar photovoltaics connected to the grid in the entire U.S. is just 473 MW at present.
"These landmark agreements signal the arrival of utility-scale PV solar power that may be cost-competitive with solar thermal and wind energy," said Jack Keenan, chief operating officer and senior vice president for utility PG&E, which made the deal, in an announcement yesterday.
Deadline: Jul 15 2013
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The Seeker for this Challenge desires proposals for chemical methods that could rapidly degrade a dilute aqueous solution
Save 66% off the cover price and get a free gift!
Learn More >>X | <urn:uuid:a5350b86-c306-450f-abc6-d3697b2e067f> | 3.46875 | 782 | Content Listing | Science & Tech. | 49.505876 |
Silicon dioxide, or silica, (SiO2) is another important example of a macromolecular solidA state of matter having a specific shape and volume and in which the particles do not readily change their relative positions.. Silica can exist in six different crystalline forms. The best known of these is quartz, whose crystal structure shown previously is shown again below.
Sand consists mainly of small fragments of quartz crystals. Quartz has a very high melting pointThe temperature at which a solid becomes a liquid. Also called freezing point., though not so high as diamond.
If you refer back to the examples on silicon, you can remind yourself of the reason that SiO2 is macromolecular. Silicon is reluctant to form multiple bonds, and so discrete molecules, analogous to , do not occur. In order to satisfy silicon’s valence of 4 and oxygen’s valence of 2, each silicon must be surrounded by four oxygens and each oxygen by two silicons. This can be represented schematically by the Lewis diagram | <urn:uuid:06274f6c-b181-4228-8040-d6b8fdde7868> | 4.03125 | 214 | Knowledge Article | Science & Tech. | 42.193631 |
Holden Crater LayersHiRISE Image PSP_001468_1535
This HiRISE image shows fine layers of light-toned rocks on the floor of Holden Crater in Margaritifer Sinus (260S, 3260E). The layers are eroded along elongated north-to-south cliffs that reveal their total thickness approaches 100 meters in some places. Individual layers can be traced for long distances along the cliffs and careful examination shows that some are less than a meter thick and can be distinguished down to the limit of the image resolution. The thickness of individual layers is best distinguished where edge-on views are afforded along large rocks that have fallen off the side of the cliff. Occurrences of such thin, uniform layered rocks that can be traced over large distances are characteristic of layers formed by deposition of sediment in lakes. It has been suggested that a lake once partially filled the crater. The eroded appearance of the layers could be due to both water and wind activity. For example, water flowing through a breach in the southwest rim may have accomplished their erosion. The fresh exposures of the layers and nearby distribution of sand ripples and dunes indicates more recent erosion is the result of wind activity. The presence of these layers that may have been deposited in an ancient lake has contributed to the proposal of this area as a target for exploration by future rovers on the surface of Mars (e.g., the 2009 Mars Science Laboratory).
Image PSP_001468_1535 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 18, 2006. The complete image is centered at -26.6 degrees latitude, 325.2 degrees East longitude. The range to the target site was 258.6 km (161.6 miles). At this distance the image scale is 25.9 cm/pixel (with 1 x 1 binning) so objects ~78 cm across are resolved. The image shown here has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 3:34 PM and the scene is illuminated from the west with a solar incidence angle of 68 degrees, thus the sun was about 22 degrees above the horizon. At a solar longitude of 137.4 degrees, the season on Mars is Northern Summer.
Images from the High Resolution Imaging Science Experiment and additional information about the Mars Reconnaissance Orbiter are available online at:
For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. | <urn:uuid:c215400c-c2ca-4ba9-9e65-3aebd31f050a> | 3.421875 | 601 | Knowledge Article | Science & Tech. | 46.250483 |
Inheritance diagram for IPython.kernel.map:
Classes used in scattering and gathering sequences.
Scattering consists of partitioning a sequence and sending the various
pieces to individual nodes in a cluster.
A class for partitioning a sequence using a map.
Returns the pth partition of q partitions of seq.
Partitions a sequence in a roun robin fashion.
This currently does not work!
Enter search terms or a module, class or function name. | <urn:uuid:50ea5204-56fc-4a54-ade6-e8d418f1d5c9> | 2.734375 | 101 | Documentation | Software Dev. | 49.884116 |
Table of Contents:
Bell, E.T. Men of Mathematics. New York: Simon and Schuster. 1967.
As Bell himself points out in his introduction, this book is not a history of mathematics. It is instead the story of the lives of a few of the thinkers who have contributed greatly to the development of modern mathematics. As such it is very useful. The stories Bell tells are always well researched and interesting, and are combined nicely with brief explanations of the mathematics that each of these men did. The mathematics is accessible to high school students. Unfortunately, the book contains only white men, but for those it does include it is an excellent resource, often going beyond the 'stock histories' to find out which anecdotes about these men are actually true. The biographies also contain a great deal of Bell's own opinions and ideas, and so to the true student of history present a very interesting source.
List of mathematicians whose biographies are contained in Men of Mathematics: Zeno, Exodus, Archimedes, Descartes, Fermat, Pascal, Newton, Leibniz, The Bernoullis, Euler, Lagrange, Laplace, Monge, Poncelet, Gauss, Cauchy, Lobatchewsky, Abel, Jacobi, Hamilton, Galois, Sylvester, Weierstrauss (Kowalewski), Boole, Hermite, Kronecker, Riemann, Kummer, Poincaré, Cantor.
Eves, Howard. Great Moments in Mathematics (Before 1650). Mathematical Association of America.
These two volumes, part of the Dolciani Mathematical Expositions Series, are a true joy to read and at the same time are very informative and very educational. Eves' style is impeccable, his explanations clear, his appreciation for mathematical beauty well expressed, and his sense of humor is pleasantly light. Okay. Now that I'm done raving about these books, I'll actually tell you about them. In all, they contain 39 'lectures' on various 'GREAT MOMENTS IN MATHEMATICS'. Taking inspiration from a pre-television-era NBC radio series called the "Music Appreciation Hour," Eves' work is not a comprehensive history of mathematics or a biographical account of mathematics. Instead it focuses on specific problems (either posed or solved) that represented great leaps forward in mathematical thought. Eves has a remarkable ability to make the most complex achievements and their relevance to the mathematical and scientific world accessible to the reader who has knowledge of some high school mathematics (some 'lectures' do not even require that). The 'moments' range from humans learning to count to the development of the abacus to Fourier series to Godel's Incompleteness Theorem. At the end of each lecture is a set of exercises that involve the mathematics learned in that lecture.
What's so great about these books is that you can just open them up to any section, start reading, and be assured that in 30 minutes you will know more mathematics, and more math history (in particular the historical significance of certain ideas and mathematical inventions). If you have a student, teacher, or friend who already has Mathematics: A Human Endeavor, (see the next page for a review), or for someone who you think would enjoy the historical slant taken here, give them these books. | <urn:uuid:e70678b7-beb9-4c3f-ab80-ee6b5ceb1bc4> | 3.0625 | 700 | Content Listing | Science & Tech. | 35.143571 |
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0.9999 = 1
0 to 0 power
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Browse High School Number Theory
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Selected answers to common questions:
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Testing for primality.
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- Which Fractions Repeat? [07/21/1998]
How do you know whether a fraction will be a repeating or terminating
decimal? If repeating, how many decimal places?
- Why Are 1^infinity, infinity^0, and 0^0 Indeterminate Forms? [05/08/1998]
Using limits to prove that 1^infinity, infinity^0, and 0^0 are
- Why Aren't There Negative Prime Numbers? [12/10/1999]
Why can't negative numbers be prime numbers?
- Why Can't 0 Divided By 0 Be 0? [11/25/2003]
Why can't you divide 0 by 0? I've thought about it and it seems that
dividing zero objects into zero groups will result in zero groups. Why
doesn't this work?
- Why Casting Out Nines Works [10/13/2008]
Can you explain in simple terms why the Casting Out Nines method works?
- Why Does 0^0 = 1 and Not Undefined? [11/30/2007]
Your proof for why x^0 = 1 uses a law which breaks down at x = 0. Then
in your definition for 0^0 you side significantly in favor of 0^0 = 1
based on your rule for x^0 = 1 (which was based on a law that breaks
down at 0). Based on what I've read I would side in favor of
undefined. Are there any more conclusive reasons for siding with 0^0 = 1?
- Why Does 0! = 1 ? [12/8/1995]
Why does 0! = 1 ?
- Why is 0! 1? [09/14/1997]
Why is zero factorial 1?
- Why Use Q and Z? [09/12/2001]
Why is the letter Q used for rational numbers and Z for integers?
- Wilson's Theorem [03/03/2002]
I'm looking for a proof for Wilson's theorem: n divides (n-1)! + 1 if and
only if n is a prime number.
- Would Aliens Use Base 10? [05/13/2002]
If aliens had 6 fingers, would they use base 12?
- Write a Sum That Totals 100 Using Digits 1 - 9 [05/30/2004]
Is it possible to arrange the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9 so that when added they total 100? Only adding is permitted and the numbers can be rearranged. Each number can only be used once.
- Writing Numbers in Bases Greater Than 10 [04/05/2001]
What would 4 x 13 [base 10] look like in base 42? Do all bases above ten
use the same method?
- Zero and Imaginary Numbers [07/18/2001]
Is it true that zero divided by an imaginary number is zero? How could
the answer be in the real number line when the divisor can't be found in
the real number line?
- Zero and Infinity [04/24/1997]
Why is the quotient of a number divided by zero infinity?
- Zero as an Exponent [7/15/1996]
Why does n^0 = 1?
- Zero as Denominator [10/22/1997]
Why can't zero be in the denominator for rational numbers?
- Zero Laws and L'Hopital's Rule [03/04/1998]
Is zero divided by zero: a) zero, b) undefined, or c) one?
- The Zero Power of Two [12/10/1998]
Why is 2 to the 0 power equal to 1? I don't understand how a number can
be multiplied by itself zero times.
- Zeros between 1 and 222 Million [11/17/2001]
How many zeros will I use if I write down all the numbers from 1 to 222
million? And how can I generalize this?
- Zero to a Negative Exponent [05/06/2001]
Is 0^(-3) equal to 0, or is it undefined? We can't determine whether to
use the 0^x = 0 rule, or to interpret it as 1/(0^3).
Search the Dr. Math Library:
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The Math Forum is a research and educational enterprise of the Drexel University School of Education. | <urn:uuid:d056eb69-03ad-4840-9d4c-7b6d032168ff> | 3.390625 | 1,080 | Q&A Forum | Science & Tech. | 91.463072 |
I need the ans with relevant figure :
Two particles P and Q, are 30m apart with Q due north of P. Particle Q is moving at 5m/s in a direction 90 deg and P is moving at 7m/s in a direction 30 deg. Find
(a) the magnitude and direction of the velocity Of Q relative to P,
(b) the time taken for Q to be due east of P,to the nearest second. | <urn:uuid:b9497b8b-5e9c-4554-88c5-9ed24130241e> | 3.1875 | 95 | Q&A Forum | Science & Tech. | 82.196 |
Date: 1993 - 1999
Are planets made out of dirt or rock? Could another planet hit earth?
Well, dirt or rock is pretty much the same thing, isn't it?
Dirt is just ground up rock...
Actually, only the inner 4 planets of our solar system (Mercury,
Venus, Earth, Mars) are mostly made of rock, like the Earth is.
The outer planets (Jupiter, Saturn, Uranus, Neptune, Pluto) are made of
"lighter" things, like hydrogen, helium, ammonia, and probably some water.
However, these planets (except Pluto) have so much of these "lighter" elements
that they are much much heavier than the Earth is.
The planets right now all orbit the sun in very nice almost circular orbits. The
diameters of those orbits differ by 10 million miles or more, and the planets
them selves are only a few thousand miles in diameter, so there's no way one
planet could come close to hitting another. The only exception to this is Pluto, that has a much
more non-circular (elliptical) orbit than any of the others, and which sometimes
crosses Neptune's orbit. Even so, they've been doing this for billions of years
and haven't collided yet, it's not likely to happen soon.
So, there's no chance of another planet hitting the Earth. In fact, we know
exactly how the planets are going to move in the future and can use computers to
calculate where they will be, and nothing very interesting at all happens for
10 millions years at least.
But there are only 9 planets, and there are probably millions of smaller objects
- asteroids and comets - in our solar system, and they will collide with the
Earth once in a while. But they won't be quite as damaging as an entire planet
Click here to return to the Astronomy Archives
Update: June 2012 | <urn:uuid:b0c41e3d-a90d-47b4-9d4a-ed0425a9be85> | 3.40625 | 410 | Knowledge Article | Science & Tech. | 56.550795 |
This is a summary from Physics World of the paper: L J Wang et al. 2000 Nature 406 277-- "Wang and colleagues begin by using a third continuous-wave laser to confirm that there are two peaks in the gain spectrum and that the refractive index does indeed change rapidly with wavelength in between. Next they send a 3.7-microsecond long laser pulse into the caesium cell, which is 6 centimetres long, and show that, at the correct wavelength, it emerges from the cell 62 nanoseconds sooner than would be expected if it had travelled at the speed of light. 62 nanoseconds might not sound like much, but since it should only take 0.2 nanoseconds for the pulse to pass through the cell, this means that the pulse has been travelling at 310 times the speed of light. Moreover, unlike previous superluminal experiments, the input and output pulse shapes are essentially the same."
I realise that the velocity of light in a medium is comprised of the phase velocity, the group velocity, and the front velocity. While the group velocity can exceed the value of c in a vacuum, the front velocity is not supposed to. The way this sounds, the front velocity is exceeding c in a vacuum by 310 times.
blue dot=phase velocity, green=group, red=front (wiki)
The wavepacket seems to exit the cell well before it enters, but the negative refractive index "forward shifts" the leading edge of the pulse. It is argued that although this is superluminal, information cannot be transmitted faster than c. Gauthier and Stenner introduced a jump discontinuity into the waveform.Its max speed was c Here is a popular account from NewScientist . What if you used one photon? What if the photon itself were the information and not a carrier? | <urn:uuid:94cf08cf-fa18-446d-8827-a3b68f0351f8> | 3.328125 | 382 | Q&A Forum | Science & Tech. | 55.174226 |
How do astronomers find planets outside our solar system?
The most successful search method used to date is called the radial velocity method. As a star is tugged to and fro by a planet's gravitational pull, astronomers measure a slight shift in the frequency of the star’s light.
Astrometry is another detection method. It is sometimes called positional astronomy. Astronomers measure a tiny shift in a star's position on the sky caused by the gravitational pull of a planet. They can use this information to calculate the planet's mass and orbit.
If a planet passes directly between a star and the observer, it blocks out a tiny portion of the star's light. This so-called transit method looks for repeated dips in a star’s light to confirm the presence of an orbiting planet.
A fourth detection method, called gravitational microlensing, comes from one of Einstein's insights in his theory of general relativity: Gravity bends space. When a planet passes in front of a more-distant star, the planet's gravity will behave like a lens to temporarily focus light from the star. This should cause a sharp increase in brightness and a change in the apparent position of the star.
Finding Earth-Like Planets
Most of the planets discovered outside our own solar system are behemoths -- worlds that are at least as massive as Jupiter, the solar system's giant.
A planet discovered by a team of astronomers led by Barbara McArthur, however, is a relative lightweight -- and perhaps a step toward detecting worlds as small as Earth. The planet orbits the star known as Rho 1 Cancri or 55 Cancri, and is the fourth planet discovered in the system.
Unlike the others in the system, which are as massive as Jupiter or even bigger, this planet probably is only around 18 times as massive as Earth -- a fraction of Jupiter's mass. Also unlike the others, it probably is rocky, and not a ball of gas like Jupiter. The planet was discovered with the Hobby-Eberly Telescope at McDonald Observatory. | <urn:uuid:aee33dfe-ee5d-4959-b75f-e065fa014eb0> | 4.0625 | 417 | Knowledge Article | Science & Tech. | 47.670287 |
|Version 2 (modified by Philip, 14 months ago) (diff)|
The material system contains many components. Artists should just care about telling actors to use appropriate materials, and occasionally creating new material XML files by copying old ones and tweaking the uniforms. Graphical programmers might care about all the various shader files.
- Models are a single mesh with a single material and texture. (Actor XML files define how meshes and materials and textures are combined to make models. Actors can use props to combine multiple models for use by a single unit, but props are completely independent as far as the rendering is concerned, so we don't need to worry about them further.)
- Shader programs contain the low-level GPU code that performs per-vertex and per-fragment computation. (These might be implemented with GLSL, or with ARB assembly programs, or with fixed-function multitexturing code - the choice of implementation language is hidden from the rest of the system.)
- Attributes are the per-vertex data that shader programs use: vertex positions, normal vectors, colors, etc. The rendering engine computes all this data.
- Uniforms are the global or per-model data that shader programs use: camera position, sun color, specular highlight power, player color, etc. Some uniforms are computed by the rendering engine; others are specified by material definitions.
- Defines are name/value strings that control the behaviour of shader programs, e.g. USE_SPECULAR=1 to activate the code that computes specular lighting. Some defines come from the rendering engine; others from materials.
- Materials refer to a shader effect and specify various defines and uniforms.
- Shader techniques define how to combine one or more shader programs and other OpenGL state (e.g. alpha-blending behaviour) to render a model. (Usually a technique only uses a single program, but sometimes it needs to perform multiple passes over each model with a different program each time.)
- Rendering modes are the different ways the renderer processes each model. E.g. first it draws each model in the shadowmap generation mode to compute shadows, and later it draws each model in the standard textured lit mode.
- Shader effects control which shader technique to use in each different context, depending on rendering mode, hardware capabilities, user-selected graphics options, etc.
Located in art/materials/. Example:
<?xml version="1.0" encoding="utf-8"?> <material> <shader effect="model_transparent"/> <alpha_blending/> <define name="USE_TRANSPARENT" value="1"/> <define name="USE_SPECULAR" value="1"/> <uniform name="specularPower" value="16.0"/> <uniform name="specularColor" value="1.0 1.0 1.0"/> </material>
Materials can contain:
- <shader effect="..."/> - refers to one of the effect XML files.
- <alpha_blending/> - required if using a shader effect that uses alpha-blending. (This causes the engine to render the model twice, in ALPHABLEND_PASS_OPAQUE and ALPHABLEND_PASS_BLEND passes, to get correct blending relative to transparent water.)
- <define name="..." value="..."/> - specifies a name/value define that is used when loading the shader. The value is typically "1" to enable an effect.
- <uniform name="..." value="..."/> - specifies a uniform value that is used when rendering models using this material. The value is between 1 and 4 space-separated decimal numbers, e.g. value="16" or value="1.0 1.0 0.0 0.5".
Set globally by engine code:
- USE_SHADOW - 1 when shadows are supported by the hardware and enabled by the user.
- USE_FP_SHADOW - 1 when GL_ARB_fragment_program_shadow is supported and enabled.
- USE_SHADOW_PCF - 1 when shadow PCF filtering is enabled.
- USE_SHADOW_SAMPLER - 1 when sampler2DShadow etc is supported in GLSL. (Unavailable on OpenGL ES.)
- SYS_HAS_ARB - 1 when GL_ARB_vertex_program/GL_ARB_fragment_program are supported, and the renderer is in shader mode.
- SYS_HAS_GLSL - 1 when GL_ARB_vertex_shader/GL_ARB_fragment_shader are supported, and the renderer is in shader mode.
- SYS_PREFER_GLSL - 1 when the preferGLSL option is enabled. (On by default on OpenGL ES.)
Set by engine code in different renderer modes:
- MODE_SHADOWCAST - 1 when rendering objects onto the shadow map. Only depth is needed, no color data.
- MODE_SILHOUETTEOCCLUDER - 1 when rendering objects that silhouettes may be displayed behind. Only depth is needed, no color data.
- MODE_SILHOUETTEDISPLAY - 1 when rendering objects that may be displayed as silhouettes. Should draw solid color playerColor.
- MODE_WIREFRAME - 1 when rendering wireframe or edged-face versions of models, for debugging.
- ALPHABLEND_PASS_OPAQUE - 1 when rendering the opaque alpha-tested pass of transparent models before water.
- ALPHABLEND_PASS_BLEND - 1 when rendering the alpha-blended pass of transparent models after water.
Set per model by engine code:
- IGNORE_LOS - 1 when the Vision component has the AlwaysVisible flag, meaning the LOS texture should not be used.
Set by materials:
- USE_OBJECTCOLOR - 1 when the objectColor uniform should be used.
- USE_PLAYERCOLOR - 1 when the playerColor uniform should be used. (Mutually exclusive with USE_OBJECTCOLOR.)
- USE_SPECULAR - 1 when specular lighting should be rendered. Requires the following uniforms:
- float specularPower - sharpness of specular highlights.
- vec3 specularColor - color and brightness (components can be larger than 1.0).
- USE_TRANSPARENT - 1 when the texture's alpha channel should be output by the fragment shader.
- DISABLE_RECEIVE_SHADOWS - 1 when shadows should not be cast onto this object. | <urn:uuid:164a8acb-a578-4c8c-81e8-a20bd2dfc448> | 2.796875 | 1,422 | Documentation | Software Dev. | 40.200433 |
Reefs in Crisis
By Barbie Bischoff
Humans have harmlessly harvested the rich wildlife on coral reefs for thousands, perhaps hundreds of thousands, of years. But in the late twentieth century, human pressures—including a population explosion and migration to coastal areas—have placed reefs at risk. In the Caribbean Basin, the population has quadrupled since 1960, and seventy-five percent of the people live within six miles of the coastline. Natural events, such as El Niño, have also played a role in the decline of reefs. And tourism has been both blessing and bane.
According to a report issued by the International Coral Reef Initiative, tourism accounts for more than fifty percent of the gross national product of several Caribbean countries; this provides an economic incentive for reef protection. But more visitors means more coral collecting and more damage caused by swimmers, divers, and boat anchors. Moreover, the clearing of land to make way for hotels and homes has greatly increased the rate of shoreline erosion. Without the natural filter provided by wetland vegetation, soil pours into the sea, blocking the sunlight vital to corals and choking the pores of sponges. Because of poor agricultural practices and wetland destruction to make way for an increasing population, reefs are getting large doses of fertilizers from agricultural runoff. The nitrogen and phosphorus in the compounds have overnutrified the water, a condition called eutrophication, and allowed fibrous and fleshy lettuce-like algae to take hold along the reefs.
The creatures that are supposed to eat algae cannot keep pace with the accelerated growth and often abandon the reef in search of a more balanced environment. Eventually, the eutrophic reef becomes a ruin as the algae thrive, starving the coral of the sunlight it needs.
Coastal waters are degraded off southern Florida, Haiti, Cuba, the Dominican Republic, and Veracruz, Mexico. Haiti’s case is acute, because only one percent of native coastal vegetation remains, and sewage treatment plants have yet to be built. Contamination from fossil fuels, industrial chemicals, and pesticides—as well as domestic and animal waste—is also a problem throughout the Caribbean.
Like other developing nations, some Caribbean countries are forced to survive by overexploiting their own resources for the global market. And coral reefs, which occupy only about 0.2 percent of the world’s oceans, supply about 9 million of the 80 million tons of fish harvested worldwide each year. Some harvesting methods, such as mechanical dredging or large-scale poisoning, irreparably damage the reefs. And overfishing has made the queen conch (a large, spiral-shelled mollusk), the spiny lobster, the whelk (a marine snail), the red snapper (a fish), and the Nassau grouper (a fish) commercially extinct in many localities. The once-abundant jewfish, a grouper, has virtually vanished from the Caribbean. In Haiti, populations of larger reef fish and lobsters are “crashing” (decreasing to very low levels) because many of these animals are taken from the sea before reaching reproductive maturity.
Commercially desirable fish and crustaceans aren’t the only casualties. Illegal sale of turtles is common in the Dominican Republic, the Bahamas, and Mexico. Tourists’ fancy for such souvenirs as shells, coral skeletons, and other curios has depleted black coral and mollusks. Meanwhile, a growing aquarium trade has overharvested smaller, ornamental fishes.
The incidence of coral disease is also climbing. And in 1997, El Niño was unexpectedly intense. This caused ocean water temperatures to rise in many reef locations. This in turn produced the worst bleaching (expulsion of the colorful algae that live within corals) seen in the last decade. In 1998, similar El Niño–caused bleaching occurred in the Great Barrier Reef off Australia’s northeastern coast.
There is the potential for good news, however. Sanctuaries are beginning to change. Formerly designed as simply small, totally protected areas, they had little impact on the health of reefs. Now the trend is to divide large areas into zones for distinct uses, such as fishing, tourism, shipping, defense, collecting, scientific research, and hunting and fishing by local residents. Florida Keys National Marine Sanctuary is among those successfully adopting this approach. Many parks throughout the Caribbean, however, don’t have the funding necessary for maintenance and enforcement.
While scientists have long recognized the importance of the land-water connection to reef health, implementation of good land management techniques is only beginning in many areas. Development within parks such as the Sian Ka’an Biosphere reserve, in the Yucatán Peninsula, is regulated. In the United States, Florida now requires barriers to control sediment generated by construction projects.
In 1997—the International Year of the Reef—a public awareness campaign, conducted on a grass-roots level, attempted to inspire local residents to protect their nearby reef ecosystems. Within the last few years, various organizations have begun to sponsor monitoring programs, mapping expeditions, scientific research, and focused conservation and management efforts
Excerpted from Natural History, December 1997-January 1998.
More About This Resource...
This online article, from The Biodiversity Crisis: Losing What Counts, walks students through the risks humans pose to the survival of coral reefs and conservation efforts. It discusses:
- Why the rate of damage to coral reefs has increased in the past century.
- The forces behind the damage“the global marketplace, fishing and tourism, and coral disease.
- Recent efforts to protect reefs, including the creation of sanctuaries, good land management, and public awareness campaigns.
Less than 1 period
Supplement a study of ecology or biodiversity with an activity drawn from this essay about the impact of humans on coral reefs.
- Ask students to brainstorm ways people put coral reefs at risk.
- Send students to this online article, or print copies of the essay for them to read.
- Have them write a one-page reaction to the article, explaining why human impact on coral reefs is so much greater than 100 years ago. | <urn:uuid:f3542184-f5a7-41a3-999e-9b58ba969485> | 3.796875 | 1,277 | Truncated | Science & Tech. | 33.083922 |
A good target for binoculars and small telescopes,
Garradd (C/2009 P1) now shines in planet Earth's
a steady performer but just
below naked-eye visibility.
images like this composite from October 15
can find the comet with a lovely green coma,
sporting multiple tails, and lingering against
a background of faint stars.
The field of view spans over 1 degree or about 2 full moons
within the southern boundaries of the constellation
Now around 16 light minutes
(2 astronomical units) away, P1 Garradd is an
intrinsically large comet, but
will never make a very close approach to Earth or the Sun
through the inner solar system.
As a result, the comet will likely stay a sight for
telescopic eyes only, moving slowly
through the sky
and remaining in Hercules during the coming months. | <urn:uuid:9f50dbc8-a97a-4df9-983a-4fa4d855ff51> | 2.984375 | 183 | Knowledge Article | Science & Tech. | 39.09875 |
Table of ContentsOverviewIntroductionMaterials and MethodsDLS of Silica SamplesResults and DiscussionConclusionsAbout Horiba
The applications of silica nanoparticles are often determined by the particle size. Dynamic light scattering provides quick, precise and repeatable nanoparticle size data and therefore is an essential tool for the nanoparticle technologist. Here, two different size silica particles are characterized with the Horiba SZ-100 in order to demonstrate the precision and utility of the instrument.
One may comfortably sip on a cold beer while listening to a MP3 player without pausing for a moment to think about those miniscule silica nanoparticles that were used to clarify the beer. Also note that the silicon wafers that constitute critical components in the mp3 player were polished flat using silica chemical mechanical polishing (CMP) nanoparticle slurries. In both these applications and many more, the size of the silica nanoparticles is a critical factor. In beer clarification, the silica is used to bind suspended haze-creating particles such as protein or yeast together forming large flocs that can be removed by settling or filtration resulting in a clear liquid. It is important that the silica particles used for CMP are not very large so as to scratch the delicate silicon wafers. However, they must be large enough to remove material quickly and cost-effectively.
Dynamic light scattering (DLS) is a preferred method for studying particles in the nano size range. Characteristics of the technique include:
- Rapid measurements, typically taking just a few minutes
- High repeatability
- Coefficient of variation on the z-average size is higher than 5% for a large number of samples
- High accuracy and is able to discern shifts in the z-average size of only a few percent
In this application note, the particle sizes of two different silica dispersions are studied to demonstrate the utility of the Horiba SZ-100 for both suppliers and users of such materials.
Figure 1. SZ-100 Nanoparticle Size Analyzer.
Materials and Methods
The samples used for the experiment include the following:
- Sample 1 used was Ludox TM 50, colloidal silica of nominal size 30 nm (narrow size distribution).
- Sample 2 was a more broadly distributed and larger-sized (nominal 500 nm) aqueous SiO2 suspension. Both materials were obtained from Sigma Aldrich. Each suspension was diluted with 10 mM KCl (aq) prior to measurement.
Figure 2. Fumed silica. The small size, hardness and inert nature of silica make it a very versatile and useful material for a wide range of applications and ideal for size analysis by DLS with the SZ-100.
DLS of Silica Samples
Dynamic light scattering information was gathered and studied with a SZ-100 particle size analyzer. Measurements were repeated five times in order to calculate the coefficient of variation, the standard deviation and mean of the measurements.
Figure 3. Sand dune. These larger silica particles, while beautiful in the aggregate, are typically analyzed by laser diffraction (HORIBA LA-950) or image analysis (HORIBA PSA300). Image courtesy of Florence Devouard and Wikimedia Commons.
Results and Discussion
The z-average diameters obtained with the SZ-100 are listed in Tables 1 and 2.
Table 1. Measurement of the Ludox TM50 colloidal silica. Here, results from two different laboratories are compared. The agreement is excellent showcasing the measurement reproducibility of the SZ-100 providing the user with confidence in multiple site installations. The SZ-100 has standardized measurement protocols which automate measurement and calculation to ensure maximum operator-to-operator and site-to-site reproducibility.
||Mean determined z-average size (nm)
Dynamic Light Scattering with SZ-100, laboratory 1
Dynamic Light Scattering with SZ-100, laboratory 2
Table 2. Measurement results for nominal 500 nm silica suspension. The two different techniques agree to within 5%, which is very good. Evident from the COV values, the measurement repeatability of the SZ-100 is superior to that the disc centrifuge.
||Particle Diameter (nm)
Manufacturer certificate (by disc centrifuge)
Dynamic Light Scattering with SZ-100
The results of these measurements show that the Horiba SZ-100 dynamic light scattering particle size analyzer can be used to characterize silica and other nanoparticle materials.
HORIBA Scientific is the new global team created to better meet customers’ present and future needs by integrating the scientific market expertise and resources of HORIBA. HORIBA Scientific offerings encompass elemental analysis, fluorescence, forensics, GDS, ICP, particle characterization, Raman, spectral ellipsometry, sulfur-in-oil, water quality, and XRF. Prominent absorbed brands include Jobin Yvon, Glen Spectra, IBH, SPEX, Instruments S.A, ISA, Dilor, Sofie, SLM, and Beta Scientific. By combining the strengths of the research, development, applications, sales, service and support organizations of all, HORIBA Scientific offers researchers the best products and solutions while expanding our superior service and support with a truly global network.
This information has been sourced, reviewed and adapted from materials provided by Horiba.
For more information on this source, please visit Horiba. | <urn:uuid:0d4f4276-e4aa-491e-9181-2884fb76a625> | 3.234375 | 1,142 | Knowledge Article | Science & Tech. | 23.450482 |
Before developing an application it needs to be somehow designed - on a piece of paper, using UML or just by creating a prototype. Another way to design the application logic is using pseudo-code.
What is pseudo-code and how to use it?
Pseudo-code is a non-formal language, a way to create a logical structure, describing the actions, which will be executed by the application. Using pseudo-code, the developer describes the application logic using his native language, without applying the structural rules of a specific programming language. The big plus of the pseudo-code is that the application logic can be easily understood by any developer in the development team (in this case, it doesnít depend, which programming language knows each team member). Also, when the application algorithm is described in pseudo-code, it is very easy to transform the pseudo-code into real code (using any programming language). For a better understanding of what is pseudo-code, letís take a look at an example. Suppose that you have to develop an application, that gets the number of students in a high school and then it gets each studentís final grade (100, 90, 80, 60 and 50) and processes the average grade for the whole school. Instead of creating the program at a computer, letís describe the application logic using pseudo-code. First, I will describe the general purpose of the application:
Process the average grade for the whole school
Now, I need to specify the fundamental actions that are needed to process the final result:
Request the number of students; Get the grade for each student; Process the average grade for the whole school;
This is a generalized description, but it describes the basic application logic. Now, I have to specify some more details (how the above actions are performed):
Application start; Declare an integer variable numberOfStudents; Declare an integer variable counter; Declare an integer variable sum; Declare a decimal variable average; Set the numberOfStudents value to 0; Set the counter value to 0; Set the sum value to 0; Request the number of students (numberOfStudents); If the entered number of students is 0 then Exit the application Else While the counter is less or equal to the number of students Get the student grade Add the student grade to the sum variable Increment the counter by 1. Get the next student information When the student information is entered, set the average variable to the result of the division (sum divided by the number of students). Show the result. Application end.
As you see, I used a human language to describe the application logic. Also, to better see the code fragments, I used a specific indentation style, so I can easily see which part of the algorithm is executing a specific action.
Some developers may think that using pseudo-code to design the application instead of creating and testing the application on the computer is a waste of time. This is true for small modules, that were created many times and which require just some small modifications to accomplish a specific task, but when it comes to large projects, itís pretty easy to be lost in the hundreds or even thousands of code lines. In this case, the pseudo-code clearly describes the application algorithms, so these can be easily implemented and it gives the developer an opportunity to think on the algorithm before implementing it. | <urn:uuid:d9e1b9e1-3b75-4063-83f6-8c130ad5cbdf> | 4.0625 | 686 | Q&A Forum | Software Dev. | 29.338026 |
Socket++ library defines a family of C++ classes that can be used more effectively than directly calling the underlying low-level system functions. One distinct advantage of the socket++ is that it has the same interface as that of the iostream so that the users can perform type-safe input output. See your local IOStream library documentation for more information on iostreams.
Socket++ was developed by Gnanasekaran Swaminathan . However, it appears that the development has ended. The latest version released by him is 1.11. Lauri Nurmi modified the source code to make Socket++ compile with recent GCC versions (under Linux, i386): "I have not added any new features, just made the code more standard-conforming" (see http://users.utu.fi/lanurm/socket++/) | <urn:uuid:59ad2788-3968-4f42-814f-82b97a859213> | 2.875 | 173 | Knowledge Article | Software Dev. | 40.958455 |
You must know that a hemisphere is a half of a sphere. Below are the formulas to find the curved surface area of a hemisphere (without the base circle area) and the total surface area of a hemisphere (with the base circle area).
Curved Surface Area of Hemisphere:
You must know that the surface area of a sphere is 4πr². A hemisphere is half of a sphere, this must mean that the curved surface area of a hemisphere is 2 divide by the surface area of a sphere. That is; 4πr²/2 which gives the following expression.
Total Surface Area of Hemisphere
If you’re to take into consideration the base circle below the curve meaning the total surface area. The surface area would be a combination of the above area and the area of the circle. As simple as that!. The area of the circle is πr². This means the total surface area is 2πr² + πr². If we simplify this gives 3πr² as expressed below.
Remember there is a difference between the curved surface area and the total surface area. The total surface area includes the base circle below the hemisphere and the curve surface area does not, it’s just the curve of the hemisphere. | <urn:uuid:15bdef17-b0e7-47fc-b852-18eb235f06ba> | 3.96875 | 257 | Tutorial | Science & Tech. | 52.462283 |
- Libraries that emulate a UNIX environment by implementing the UNIX Application Programming Interface (API)
- Include files and development tools such as cc(1), yacc(1), lex(1), and make(1).
- ksh(1) (the Korn Shell) and over 250 utilities such as ls(1), sed(1), cp(1), stty(1), etc.
Most of the UNIX API is implemented by the POSIX.DLL dynamically loaded (shared) library. Programs linked with POSIX.DLL run under the WIN32 subsystem instead of the POSIX subsystem, so programs can freely intermix UNIX and WIN32 library calls. A cc(1) command is provided to compile and link programs for UWIN on Windows using traditional UNIX build tools such as make(1). The cc(1) command is a front end the the underlying compiler that performs the actual compilation and linking. It can be used with the Microsoft Visual C/C++ 5.X compiler, the Visual C/C++ 6.X compiler, the Visual C/C++ 7.X compiler, the Digital Mars C/C++ compiler, compiler, the Borland C/C++ compiler, and the Mingw compiler. The GNU compiler and development tools are also available for download to UWIN.
UWIN runs best on Windows W7/VI/XP/NT/2000 with NTFS, but will run in degraded mode with the FAT file system, and further degradation with Windows ME/98/95.
AT&T's Research Projects page
This post has been edited by patchworks: 17 June 2012 - 02:37 AM | <urn:uuid:726e071d-7d9f-4c33-9971-c7df86ee95a4> | 2.703125 | 345 | Knowledge Article | Software Dev. | 71.987835 |
WINTER ice can severely disrupt shipping around northern coastlines. But now a Canadian marine engineer claims he has found a way of controlling ice formation in ports and harbours. Per Andersen says his wave generator projector could help prevent seawater from freezing over by producing artificial waves.
When seawater is mechanically agitated, the deeper, warmer water mixes with the colder surface water. This process should prevent ice from building up, says Andersen, who has tested the prototype in Canada.
The machine is 7.5 metres long. It consists of a floating helical roller, similar to a large corkscrew, supported at either end by pontoons. The roller is rotated in the water by an electric motor to create a train of waves several hundred millimetres high.
According to Andersen, artificial waves have a higher height-to-length ratio than natural waves, making them better able to displace water. As a result, more water is ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:f04996da-7a7c-43e9-9706-e05cdffb215d> | 3.734375 | 218 | Truncated | Science & Tech. | 42.555256 |
The CLOUD collaboration from CERN finally had their results published in nature
, showing that ionization increases the nucleation rate of condensation nuclei. The results are very beautiful and they demonstrate, yet again, how cosmic rays (which govern the amount of atmospheric ionization) can in principle have an affect on climate.
What do I mean? First, it is well known that solar variability has a large effect on climate. In fact, the effect can be quantified and shown to be 6 to 7 times larger than one could naively expect from just changes in the total solar irradiance. This was shown by using the oceans as a huge calorimeter (e.g., as described here
). Namely, an amplification mechanism must be operating.
One mechanism which was suggested, and which now has ample evidence supporting it, is that of solar modulation of the cosmic ray flux, known to govern the amount of atmospheric ionization. This in turn modifies the formation of cloud condensation nuclei, thereby changing the cloud characteristics (e.g., their reflectivity and lifetime). For a few year old summary, take a look here
So, how do we know that this mechanism is necessarily working? Well, we know that cosmic rays have a climatic effect because of clear correlations between unique cosmic ray flux variations and different climate variability. One nice example (and not because I discovered it ;-) ) is the link between cosmic ray flux variations over geological times scales (caused by spiral arm passages) and the appearance of glaciations (more about it here
). We also know empirically that the effect of the cosmic rays is through the tampering in the properties of cloud. This is through the study of Forbush decreases which are several day long decreases in the galactic cosmic ray flux reaching the Earth. Following such events, one clearly sees a change in the aerosol and cloud properties (more about it here
So, what is new?
Well, the new results just published in nature by Kirkby and company are the results of the CLOUD experiment. This experiment mimics the conditions found in the atmosphere (i.e., air, water vapor, and trace gasses, such as sulfuric acid and ammonia). It is a repeat of the Danish SKY experiment carried out by Henrik Svensmark and his colleagues (e.g., read about it here
), and it produces the same results—namely, they show that an increase in the rate of atmospheric ionization increases the formation rate of condensation nuclei. The only difference is that the CLOUD experiment with its considerably higher budget, has a better control on the different setup parameters. Moreover, those parameters can be measured over a wider range. This allows the CLOUD experiment to more vividly see the effect.
The results can be seen in this graph:
What does it mean?
The first thing to know is that when 100% humidity is reached in pure air, clouds don't form just like that. This is because there is an energy barrier for the droplets to form. To get over this barrier, the water vapor condenses on small particles called cloud condensation nuclei (CCNs). Some of these CCNs can be naturally occurring particles, such as dust, biologically produced particles, pollution or sea salts. However, over a large part of the globe, most of the CCNs have to be grown from basic constituents, in particular, clusters of sulfuric acid and water molecules. As the CLOUD and SKY experiments demonstrate, the ionization helps stabilize the clusters, such that they can more readily grow to become stable "condensation nuclei" (CNs). These CNs can later coalesce to become the CCNs upon which water vapor can condense.
Moreover, the number density of CCNs can clearly have an effect on different cloud properties. This can be readily seen by googling "Ship Tracks" where more CCNs (in the form of exhaust particles) serve as extra CCNs (You can also read about it here
It should be stressed that although the results are extremely impressive (it is a hard measurement because of the very precise control over the conditions which it requires), they are not new, just a formidable improvement. This implies that anyone who chose to ignore all the evidence linking solar activity, through cosmic ray flux modulation, to climate change, and the evidence demonstrating that the link can be naturally explained as ion induced nucleation
, will continue to do so now. For example, you will hear the real climate guys down playing it as much as possible.
Ok, so what do these results imply?
The first point was essentially pointed above. The results unequivocally demonstrate that atmospheric ionization can very easily affect the formation of condensation nuclei (CNs). Since many regions of earth are devoid of natural sources for CCNs (e.g., dust), the CCNs have to grow from the smaller CNs, hence, the CCN density will naturally be affected by the ionization, and therefore, the cosmic ray flux. This implies that ion induced nucleation
is the most natural explanation linking between observed cosmic ray flux variations and climate. It has both empirical and beautify experimental results to support it.
Second, given that the cosmic ray flux climate link can naturally be explained, the often heard "no proven mechanism and therefore it should be dismissed" argument should be tucked safely away. In fact, given the laboratory evidence, it should have been considered strange if there were no
empirical CRF/climate links!
Last, given that the CRF/climate link is alive and kicking, it naturally explains the large solar/climate links. As a consequence, anyone trying to understand past (and future) climate change must
consider the whole effect that the sun has on climate, not just the relatively small variations in the total irradiance (which is the only solar influence most modelers consider). This in turn implies (and I will write about it in the near future), that some of the 20th century warming should be attributed to the sun, and that the climate sensitivity is on the low side (around 1 deg increase per CO2
Oh, and of course kudos to Jasper Kirkby and friends! | <urn:uuid:23426049-b704-499e-b1ae-84bc7d80a8a6> | 3.09375 | 1,273 | Comment Section | Science & Tech. | 41.810865 |
Nov. 14, 2009 The Sun is a bubbling mass. Packages of gas rise and sink, lending the sun its grainy surface structure, its granulation. Dark spots appear and disappear, clouds of matter dart up -- and behind the whole thing are the magnetic fields, the engines of it all. The SUNRISE balloon-borne telescope, a collaborative project between the Max Planck Institute for Solar System Research in Katlenburg-Lindau and partners in Germany, Spain and the USA, has now delivered images that show the complex interplay on the solar surface to a level of detail never before achieved.
The largest solar telescope ever to have left Earth was launched from the ESRANGE Space Centre in Kiruna, northern Sweden, on June 8, 2009. The total equipment weighed in at more than six tons on launch. Carried by a gigantic helium balloon with a capacity of a million cubic metres and a diameter of around 130 metres, SUNRISE reached a cruising altitude of 37 kilometres above the Earth's surface.
The observation conditions in this layer of the atmosphere, known as the stratosphere, are similar to those in outer space: for one thing, the images are no longer affected by air turbulence; and for another, the camera can also zoom in on the Sun in ultraviolet light, which would otherwise be absorbed by the ozone layer. After separating from the balloon, SUNRISE parachuted safely down to Earth on June 14th, landing on Somerset Island, a large island in Canada's Nunavut Territory situated in the Northwest Passage, the seaway through the Arctic Ocean between the Atlantic and the Pacific.
The work of analysing the total of 1.8 terabytes of observation data recorded by the telescope during its five-day flight has only just begun. Yet the first findings already give a promising indication that the mission will bring our understanding of the Sun and its activity a great leap forward. What is particularly interesting is the connection between the strength of the magnetic field and the brightness of tiny magnetic structures. Since the magnetic field varies in an eleven-year cycle of activity, the increased presence of these foundational elements brings a rise in overall solar brightness -- resulting in greater heat input to the Earth.
The variations in solar radiation are particularly pronounced in ultraviolet light. This light does not reach the surface of the Earth; the ozone layer absorbs and is warmed by it. During its flight through the stratosphere, SUNRISE carried out the first ever study of the bright magnetic structures on the solar surface in this important spectral range with a wavelength of between 200 and 400 nanometres (millionths of a millimetre).
"Thanks to its excellent optical quality, the SUFI instrument was able to depict the very small magnetic structures with high intensity contrast, while the IMaX instrument simultaneously recorded the magnetic field and the flow velocity of the hot gas in these structures and their environment," says Dr. Achim Gandorfer, project scientist for SUNRISE at the Max Planck Institute for Solar System Research.
Previously, the observed physical processes could only be simulated with complex computer models. "Thanks to SUNRISE, these models can now be placed on a solid experimental basis," explains Prof. Manfred Schüssler, solar scientist at the MPS and co-founder of the mission.
In addition to the Max Planck Institute for Solar System Research, numerous other research facilities are also involved in the SUNRISE mission: the Kiepenheuer Institute for Solar Physics in Freiburg, the High Altitude Observatory in Boulder (Colorado), the Instituto de Astrofisica de Canarias on Tenerife, the Lockheed-Martin Solar and Astrophysics Laboratory in Palo Alto (California), NASA's Columbia Scientific Ballooning Facility and the ESRANGE Space Centre. The project is funded by the Federal Ministry of Economics through the German Aerospace Centre (DLR).
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Note: If no author is given, the source is cited instead. | <urn:uuid:1ef22685-5bf9-4c3f-bc87-1d8c0ea2ba60> | 4 | 838 | Truncated | Science & Tech. | 30.830404 |
August 7, 2012 | 16
NASA's Mars Reconnaissance Orbiter, which yesterday delivered a stunning photo of the Curiosity rover descending on its parachute toward a safe landing, has followed up with another look at the mobile laboratory.
The orbiter's High-Resolution Imaging Science Experiment camera, or HiRISE, can zoom in on Mars to photograph surface features less than a meter in length. HiRISE's superior visual acuity has enabled it to spot other small Mars robots, such as NASA's Spirit and Opportunity rovers, even as it zooms along in orbit some 300 kilometers overhead.
Curiosity, at three meters long and 2.8 meters wide, is nearly twice the length of Spirit or Opportunity. So HiRISE was able to photograph the newly arrived Curiosity, along with the discarded rocket-powered platform (the "sky crane") that had lowered the rover to the surface. Also visible in the photo is the spacecraft's thermal shield, which protected the rover from intense friction-generated heat during its entry into the Martian atmosphere at more than 20,000 kilometers per hour, as well as the parachute that further slowed the rover's entry before the sky crane took over.
The massive rover touched down at 1:31 A.M. Eastern Daylight Time on August 6, beginning its mission of exploration at Gale Crater. Inside the 150-kilometer-wide basin, Curiosity will investigate the chemical and geologic record of Mars's past climate, with an eye toward determining whether the Red Planet was ever hospitable to life.
Deadline: Jul 15 2013
Reward: $5,000 USD
SciBX: Science-Business eXchange, a joint publication from the makers
Deadline: Jul 25 2013
This challenge provides an opportunity for Solvers to build a web-based or mobile “app” to explore data relationships in scholarly conte
Get Both Print & Tablet Editions for one low price!X | <urn:uuid:afcfe746-687b-4d78-a305-eb1f1f179f30> | 3.515625 | 397 | Truncated | Science & Tech. | 35.091369 |
|Oracle® OLAP DML Reference
10g Release 1 (10.1)
Part Number B10339-02
REMBYTES(text-expression start [length])
The expression from which REMBYTES removes bytes. When the characters to be removed from text-expression contain embedded line breaks, these breaks are also removed. Other line breaks are preserved. Removed line breaks are not counted toward the total number of characters removed.
An integer that represents the character position at which to begin removing characters. The position of the first character in text-expression is
1. When the value of start is greater than the length of text-expression, REMBYTES simply returns text-expression.
An integer that represents the number of characters to be removed. When length is not specified, only the character at start is removed.
When you are using a single-byte character set, you can use the REMCHARS function instead of the REMBYTES function.
This function does not accept NTEXT arguments, because it is oriented toward byte-manipulation instead of character manipulation. It always returns values of type TEXT. When you must use this function on NTEXT values, use the CONVERT or TO_CHAR function to convert the NTEXT value to TEXT.
Example 20-15 Using REMBYTES to Remove a Substring
This example shows how to remove the substring
there from the text value
SHOW REMBYTES('hellotherejoe', 6, 5)
produces the following output. | <urn:uuid:48f2d364-8067-464c-83d1-739a080c796e> | 3.234375 | 321 | Documentation | Software Dev. | 47.404452 |
by Staff Writers
Washington (UPI) Aug 21, 2012
The ongoing U.S. drought may have one bright side, researchers said, as a record-low number of tornadoes have been recorded.
While drought and hot, dry weather has devastated agriculture this summer and led to the deaths of dozens of people, it has also decreased the outbreaks of tornadoes, scientists at the National Severe Storms Laboratory of the National Atmospheric and Oceanic Administration said.
Around 300 tornadoes have hit the U.S. since the middle of April, the fewest in that time period in nearly 60 years of record-keeping, they said.
That's about a third of the average major tornado incidents for the period.
"This is a really rare event," Harold Brooks, a research meteorologist at the storm laboratory, told The Wall Street Journal.
"The simple reason is: You aren't going to get a tornado if you don't have thunderstorms."
A high-pressure system has been parked over the middle of the United States, bringing oppressive heat but keeping severe storms with their precipitation -- conditions which can spawn tornadoes -- at bay.
July, the warmest month on record for the United States, saw the fewest tornadoes ever recorded for the month.
The simple fact, Dan Kottlowski, a senior meteorologist with Accuweather.com, told the Journal, is that rainfall brings tornadoes while drought keeps them away.
"Which side of the coin do you want?" he said.
Climate Science News - Modeling, Mitigation Adaptation
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Mayans made drought worse with crops
New York (UPI) Aug 21, 2012
Mayans may have hastened the demise of their civilization by clearing forests, making an already naturally drying climate drier, U.S. scientists say. Prolonged drought is thought to have contributed to the eventual collapse of Mayan civilization in Mexico and Central America, and forest razing for cities and agriculture may have made matters worse, the researchers said. "We're no ... read more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement| | <urn:uuid:537a3930-07ae-470d-89bf-3b2cda489426> | 3.171875 | 564 | Truncated | Science & Tech. | 45.351363 |
The cold temperatures maintained in the Trinity River are beneficial to fish but may be problematic for foothill yellow-legged frogs. TRRP assesses foothill yellow-legged frog breeding distribution, timing, and survival of egg masses. In 2009, 50 egg masses detected in the mainstem river between Lewiston Dam and the North Fork Trinity River. This was the highest count since egg mass surveys began in 2004, and several of the breeding sites were at restoration sites below Canyon Creek . However, it is still minimal compared to some tributaries. Tributaries and the mainstem with colder water had later onset of egg laying and emergence of smaller froglets when compared to warmer tributaries. While relative abundance on the mainstem has increased over the previous four years, reproductive effort is still substantially less than observed on the South or North Fork Trinity River.
Suggested further reading:
Fuller, T E; Pope, K L; Ashton, D T; and Welsh, H H Jr (2010) Linking the distribution of an invasive amphibian (Rana catesbeiana) [bullfrogs] to habitat conditions in a managed river system in northern California.
Ashton, D T; Bettaso, J B; and Welsh, H H Jr (2010) Foothill yellow-legged frog (Rana boylii) distribution and phenology relative to flow management on the Trinity River. Oral presentation provided at the 2010 Trinity River Science Symposium
Lind, A J; Welsh, H H Jr; and Wilson, R A (1996) The effects of a dam on breeding habitat and egg survival of the foothill yellow-legged frog (Rana boylii) in northwestern California.
Wilson, R A; Lind, A J; and Welsh, H Jr (1991) Trinity River riparian wildlife survey – 1990. | <urn:uuid:27c6907d-1ccf-449f-bd2c-3eba87fe018b> | 3.3125 | 375 | Knowledge Article | Science & Tech. | 43.319956 |
Have you noticed bright lights in the western sky, soon after sunset? Maybe you heard something somewhere about a planetary alignment. Maybe the Weekly World News you glanced at (first looking around to make sure nobody was watching) in the checkout line said something about the alignment, Bat Boy, Mel Gibson and the Mayan Calendar Apocalypse. Well, there are some pretty goings on in the western sky, at least that much is true. Here’s the skinny:
The planets Venus and Jupiter, easily noticeable since they are two of the brightest “stars” in the night sky, are approaching each other, or rather, they appear to be approaching each other from our vantage point, and they’ll appear to draw nearer to one another until March 14th, when we’ll all start to get really suspicious that something is going on between those two.
Here’s a representation of the relative positions of the planets on February 24th. This model is based on the Copernican model, which places the sun at the center of the solar system (and placed Galileo in hot water with the Church). Believers in other cosmological models, please stop reading and whatever you do, don’t look at the image below, it’s obscene. For everyone else, rationally note that the following image is not remotely to scale. The planets are proportionally correct in relation to each other, in other words, Mercury is smaller than Venus, and Mars is smaller than Earth, and Jupiter (and the Sun) are bigger than all of them, but that’s as much as you can say. The orbits are condensed and not proportional, except that Jupiter is much farther out than the inner planets. That’s why they are inner planets and it is the first of the outer planets! Most importantly, the planets are positionally more or less correct for March 2012 so we can at least see a rough approximation of the geometry at work here. Gosh, this almost took longer to introduce than it did to draw in Illustrator.
If you draw a triangle between Earth, Jupiter and Venus and you get an idea of how we perceive the conjunction. As Jupiter moves (in this image clockwise) in its orbit, the angle Jupiter-Earth-Venus narrows. Venus is moving clockwise as well, but from earth it appears to be receding, whereas Jupiter appears to be dropping towards the Sun. Let’s add an observer to the surface of the earth, in a position just after sunset.
You get the idea. The angle Jupiter-Bicycle Astronomer-Venus is much smaller than, say, Mars-Bicycle Astronomer-Jupiter. Indeed, Mars and Jupiter are on opposite sides of the evening sky. Venus and Jupiter are “setting” in the West, appearing to follow the Sun, while over the Bicycle Astronomer’s shoulder, Mars is “rising” in the East, the brightest reddish “star” in that direction. Here is the Bicycle Astronomer up close:
As I wrote above, the angular separation of the nightmare greenhouse gas planet of Venus and truly giant gas giant Jupiter will appear to shrink until March 14th. Ten days later, a thin waxing crescent moon will appear near the horizon below them, and our couple will, well, get a little more complicated. Mark your calendars and wander outside when you’re finished with your supper, and look west. The conjunction is pretty much an optical trick caused by the geometry of the clockwork solar system, but it’s still really pretty. It shouldn’t cause the end of the world, either.
Here’s a nicely-made video by Nasa about the conjunction, which also explores why exactly it might appear so strikingly beautiful to us, a theme I’ll pick up in the next post. | <urn:uuid:3e2572d8-2e17-47b1-a02e-9fbdccda2d0c> | 2.828125 | 799 | Personal Blog | Science & Tech. | 50.03699 |
This week's highlight taxon is the Aquificae. Aquificae is a smallish group of thermophilic to hyperthermophilic bacteria whose main claim to fame is that ribosomal DNA phylogenies suggest that it is the earliest-diverging branch of the Eubacteria, making them a key player in the theory that life as a whole may be descended from a thermophilic ancestor. The type genus of the Aquificae, Aquifex (A. aeolicus shown above in an image from here), was only formally described in 1992, but the numbers have swelled since then to about fifteen genera divided between three families. Because their thermophilic habits make them difficult to culture, the diversity of Aquificae is almost certainly underestimated. Environmental molecular analyses, for instance, indicate that near neutral pH terrestrial thermal springs may be dominated by Aquificae, while examples of Aquificae have been isolated from deep-sea, shallow marine and terrestrial hydrothermal systems, subsurface mines, and even heated compost (Aguiar et al., 2004). Aquificae found in thermal springs form extensive microbial mats stained black or yellow by iron or sulphur mineral deposits, leading to their being referred to as "black filaments" or "sulphur-turf".
Aquificae are all chemolithoautotrophs - that is, they produce their own energy directly from the reaction of inorganic sources. This is acheived through the oxidation of molecular hydrogen, which is a major component of emissions from deep-sea hydrothermal vents. Aquifex reacts hydrogen and oxygen to produce water, while other species of Aquificae use such substrates as elemental sulphur or nitrates as electron acceptors. Hydrogen oxidation is a common metabolic process in archaebacteria, but is unusual in eubacteria - the only hydrogen-oxidising eubacteria other than Aquificae belong to the ε-proteobacteria. Aquificae may be anaerobes or microaerophiles.
Phylogenetically, Aquificae are actually something of a puzzle. As already noted, the ribosomal DNA phylogenies place the Aquificae basal to all other eubacterial groups. However, it has been fairly conclusively shown that the eukaryote section of the rDNA tree is quite severely compromised by long-branch attraction, and it is quite possible that the bacterial section of the tree suffers the same problem. In the case of the Aquificae, there is evidence that they may not be as basal as they appear.
Bacteria can be divided into two major groups, the Gram-positive and Gram-negative bacteria. While this originally referred only to the ability of the bacterium to be stained with Gram's iodine and crystal violet, the results actually reflect a far more fundamental distinction between the two groups. Gram-positive bacteria have a single cell membrane surrounded by a thick cell wall. Gram-negative bacteria, on the other hand, have a thinner cell wall with a second membrane overlying it. Many molecular phylogenetic trees also show a sort of rough division between the two groups, with Gram-positive bacteria tending to sit closer than Gram-negative bacteria to the archaebacteria and eukaryotes, which like Gram-positive bacteria have a single cell membrane. Gupta (1998) formalised this distinction by dividing prokaryotes between the Monodermata (Gram-positive bacteria and archaebacteria) and Didermata (Gram-negative bacteria), suggesting only a single loss or gain (depending on where exactly the root of the tree of life sits) of the second cell membrane.
Aquificae, however, are Gram-negative, complete with second cell membrane. If their position on the ribosomal DNA trees is accurate, this would require either that the outer membrane was gained or lost multiple times. If the membrane gain or loss was a unque event, then Aquificae must be closer to the other Gram-negative bacteria. Cavalier-Smith (2002) placed Aquificae in a position within or near the Epsilonproteobacteria, as suggested by RNA polymerase and a few other molecular phylogenies. As already mentioned, it is notable that ε-proteobacteria include the only other hydrogen-oxidising eubacteria (Takai et al., 2003). Insertions in the alanyl-tRNA synthetase and RNA polymerase β genes also support a position for Aquificae among the other Gram-negative bacteria, possibly close to the Proteobacteria. It seems possible (though it must be stressed that it is far from well-established) that the rDNA tree has been compromised by long-branch attraction, probably due to the high G+C content of the Aquificae genome, which is itself believed to be an adaptation to a thermophilic lifestyle.
Aguiar, P., T. J. Beveridge & A.-L. Reysenbach. 2004. Sulfurihydrogenibium azorense, sp. nov., a thermophilic hydrogen-oxidizing microaerophile from terrestrial hot springs in the Azores. International Journal of Systematic and Evolutionary Microbiology 54: 33-39.
Cavalier-Smith, T. 2002. The neomuran origin of archaebacteria, the negibacterial root of the universal tree and bacterial megaclassification. International Journal of Systematic and Evolutionary Microbiology 52: 7-76.
Gupta, R. S. 1998. Life's third domain (Archaea): an established fact or an endangered paradigm? A new proposal for classification of organisms based on protein sequences and cell structure. Theoretical Population Biology 54 (2): 91-104.
Takai, K., S. Nakagawa, Y. Sako & K. Horikoshi. 2003. Balnearium lithotrophicum gen. nov., sp. nov., a novel thermophilic, strictly anaerobic, hydrogen-oxidizing chemolithoautotroph isolated from a black smoker chimney in the Suiyo Seamount hydrothermal system. International Journal of Systematic and Evolutionary Microbiology 53: 1947-1954. | <urn:uuid:ee19a2bc-c093-41ed-84ab-959fa7d8fccf> | 3.921875 | 1,305 | Knowledge Article | Science & Tech. | 27.794741 |
INTRODUCTION TO OPHIOLITES
by Akira ISHIWATARI
(Dr., Assoc. Prof., Fac. Sci., Kanazawa University)
[Ishiwatari's Home Page] [Ishiwatari Labo Page] [Earth Science Department Page]
1. Ophiolite and Oceanic Lithosphere
2. Ophiolite Examples and their Occurrences
3. Petrologic Classification of Ophiolites
4. Ophiolites in the Circum-Pacific Orogenic Belts
5. Ophiolite Pulses
6. Ophiolite Belts on the Earth
1. Ophiolite Succession and Seismic Layers of Oceanic Crust
2. Pre-Cretaceous Tectonic Units of the Inner Zone of southwestern Japan
3. Modal Variation of Residual Mantle Peridotite with Increasing Degree of Melting
4. Petrologic Types of Ophiolite
5. Geologic Structure of the Klamath Mountains, western USA
6. Histogram of Formation Ages of Ophiolites in the World
7. Ophiolite Belts in the World
1. Ophiolite and oceanic lithosphere
Ophiolite is a stratified igneous rock complex composed of upper basalt member, middle gabbro member and lower peridotite member (Fig. 1). Some large complexes measure more than 10 km thick, 100 km wide and 500 km long. The term "ophiolite" means "snake stone" in Greek. Basalt and gabbro are commonly altered to patchy green rocks, and peridotite is mostly changed into black, greasy serpentinite. The term comes from such serpentine appearance of these altered, metamorphosed, or sometimes highly fragmented members.
Ophiolite is interpreted to be thrust sheet of ancient oceanic lithosphere which has been obducted over the continental crust in the course of orogeny. The ophiolite succession can be correlated with the seismologic layering of the oceanic lithosphere (Fig. 1). The sedimentary cover correspond to Layer 1, basaltic pillow lava matches Layer 2, sheeted dikes and gabbro with occasional plagiogranite intrusions are correlated to Layer 3, and ultramafic cumulates and residual mantle peridotite represent Layer 4 (mantle).
Figure 1 (BACK)
2. Ophiolite examples and their occurrences
Ophiolite was first described from the Alps in the early 20th century, and was later discovered from almost every orogenic belt on the earth. Semail ophiolite in Oman (Mesozoic), Troodos ophiolite in Cyprus (Mesozoic), Papua ophiolite in Papua-New Guinea (Mesozoic), and Bay of Islands ophiolite in Newfoundland (Paleozoic) are the best known. Yakuno (Paleozoic), Horokanai (Mesozoic) and Poroshiri (Mesozoic) are the three full-membered ophiolites in Japan, which also has many dismembered ophiolites such as Oeyama (Paleozoic), Miyamori (Paleozoic), Mikabu (Mesozoic) and Setogawa-Mineoka (Cenozoic).
Ophiolite occurs as a nappe (intact thrust sheet) or as a melange (tectonic mixture of fragments). In collisional orogenic belts, ophiolites generally lie on older continental basement. In circum-Pacific orogenic belts, however, ophiolites generally lie on younger accretionary complexes. For example, Jurassic Tamba accretionary complexes are overlain by the late Paleozoic Yakuno ophiolite, which is in turn overridden by the early Paleozoic Oeyama ophiolite (Fig. 2). The younger Mikabu and Setogawa-Mineoka ophiolites underlies the Jurassic accretionary complexes in the Pacific coastal areas.
Figure 2 (BACK)
3. Petrologic classification of ophiolites
Ophiolites may have formed either at divergent plate boundaries (mid-oceanic ridges) or convergent plate boundaries (supra-subduction zones; i.e. island arcs and marginal basins). They are called MOR and SSZ types, respectively. These types are identified by chemical composition of the rocks and minerals in comparison with those from various tectonic settings on the earth at present.
Ophiolitic mantle peridotite is the refractory residue after extraction of basaltic melt through partial melting processes in the mantle. Although primary mantle peridotite may be lherzolite with abundant clinopyroxene, it changes into clinopyroxene-poor (or -free) harzburgite as the degree of melting increases (Fig. 3). The mantle peridotite samples dredged from the mid-oceanic ridges are mostly lherzolite, while those dredged from supra-subduction zones (trench walls) are mostly harzburgite.
Figure 3. (BACK)
Ophiolitic igneous cumulates shows systematic variation in the crystallization sequence of minerals corresponding to the petrologic diversity of the underlying peridotite mantle. The mineral crystallizing next to olivine varies from plagioclase through clinopyroxene to orthopyroxene as the degree of melting in the underlying mantle increases (Fig. 4). The characteristic cumulate rocks correspondingly varies from troctolite through wehrlite to harzburgite.
In general, ophiolitic basalt also varies from alkali basalt or high-alumina basalt (like mid-ocean ridge basalt (MORB)) through low-alumina basalt (like island-arc tholeiite (IAT))to boninite (high-magnesian andesite) in correspondence with the petrologic variation of the underlying members (Fig. 4).
Figure 4. (BACK)
4. Ophiolites in the circum-Pacific orogenic belts
Ophiolites in the circum-Pacific orogenic belts generally occur intercalated among the accretionary complexes and show multiple tectonic superposition as exemplified by the Klamath Mountains in western USA (Fig. 5). The oldest early Paleozoic ophiolite occupies structurally uppermost position, and younger ones take lower seats. Such "Confucian" ophiolite belts are also present in Japan and northeastern Russia, and forms "circum-Pacific Phanerozoic multiple ophiolite belts". This structure may be formed by underplating of the accreted oceanic material and trench-fill sediments beneath the overlying SSZ lithosphere (ophiolite) and subsequent underplating of the younger SSZ-trench system. The circum-Pacific ophiolite belts are also characterized by extreme petrologic diversity. Juxtaposition of depleted, clinopyroxene-free harzburgite and fertile lherzolite is common, though such a case is rare in the collisional orogenic belts.
Figure 5. (BACK)
Reported formation ages of ophiolites show three distinct peaks at about 750, 450 and 150 Ma, respectively (Fig. 6). These are called ophiolite pulses. Each pulse corresponds to the period of worldwide magmatic event as represented by voluminous granite intrusions.
Production rate of oceanic crust was distinctly high during the 80 and 120 Ma interval of Cretaceous time, as evidenced by wide area of the ocean floor formed in this interval. Magnetic reversals of the earth, which take place every million years, were unreasonably absent during this interval. These facts lead Larson (1991) to a hypothesis of superplume, a big plume of hot mantle rock which ascended from core/mantle boundary and erupted beneath the South Pacific ocean during this interval, causing worldwide magmatic event. This interval corresponds to the later half of the Mesozoic ophiolite pulse (Fig. 6).
Figure 6. (BACK)
6. Ophiolite belts on the earth
Ophiolites issued by each pulse tend to form a particular ophiolite belt. Late Proterozoic (ca. 750 Ma) ophiolites are distributed in the Pan-African orogenic belt, early Paleozoic (ca. 450 Ma) ophiolites appear in the Appalachian-Caledonian-Uralian belt, and Mesozoic (ca. 150 Ma) ophiolites dominate the Alpine-Himalayan belt (Fig. 7). However, the circum-Pacific orogenic belts bear ophiolites of widely varying ages, including at least two pulses (early Paleozoic and Mesozoic). This may be due to continuous, subduction-induced, accretionary orogeny that have taken place in the circum-Pacific areas from early Paleozoic to the present, showing contrast to the episodic, short-lived, collisional orogeny in the continental areas. Circum-Pacific ophiolites may be the best witnesses of the history of superplumes.
Figure 7. (BACK)
Established 99/02/03, Revised 01/11/24. | <urn:uuid:b76a0513-f2a5-4dbd-b5ee-e2d5e0df3eed> | 3.59375 | 2,007 | Academic Writing | Science & Tech. | 21.58901 |
The atomic rates for H and He-like ions are accurate for densities up to cm by taking into account the effects of 3-body recombination and lowering of the continuum ([Bautista et al. 1998], [Bautista et al. 1999]). However, these effects are not treated for other species which reduce the accuracy of the model results for these ions at high density. The density for which these effects become important for a given ion increases rapidly with effective charge of the ion, starting at about cm for z=1 and at about cm for z=8. At low densities numerical errors can occur; the user is urged to read chapter 6. | <urn:uuid:5d758d71-16f4-4c92-80f7-fd9a1e8d9ff5> | 2.703125 | 134 | Documentation | Science & Tech. | 55.441284 |
Herschel offers two types of spectroscopic capability. PACS and SPIRE offer low to intermediate resolution spectroscopy covering the full Herschel wavelength range. HIFI offers high-resolution spectroscopy over the range from 157-625 μm (480-1910 GHz) using heterodyne techniques, although there is a small gap in coverage from 213-240 microns (1272-1430 GHz), between the HIFI 5b and 6a sub-bands. Users can thus be able to select a wide range of resolutions from Δλ/λ=20 to Δλ/λ=10 000 000 according to the brightness of their source and the science that is required. The main spectroscopic capabilities are summarised in Table 3.2.
In its highest resolution mode Herschel offers a velocity resolution as high as 0.3km/s. The wavelength range covered by Herschel has many thousands of lines of water, atomic transitions and organic molecules. This allows Herschel to study the chemistry of the interstellar medium, tracing water and organic molecules in molecular clouds. Herschel is also be able to study the chemistry of solar system bodies such as the atmosphere of Mars and the comas of comets in unprecedented detail.
All three instruments have a mapping capability in spectroscopic mode, even though HIFI's is somewhat limited, although by no means negated, by the fact that its detector has only a single pixel. PACS and HIFI can scan the detectors across the sky, accumulating spectroscopic data along the length of the scan. SPIRE cannot do that, instead it uses a beam-steering mirror to make filled maps. All three instruments can make a raster map in spectroscopic mode. This allows a spectroscopic survey to be made either of a region that has been mapped in imaging mode, such as a cluster of galaxies, or across a known extended source such as a molecular cloud.
Table 3.2. The main spectroscopic capabilities of PACS, SPIRE and HIFI. For more details please check the relevant instrument manual.
|Wavelength range||55-210 μm||194-313 and 303-671 μm||157-213 and 240-625 μm (with gap)|
|Field of view||47x47"||2.0' (unvignetted)||Single pixel (see below)|
|Pixel size||9"||17", 29" (varies across the bands)||39" (488GHz), 13" (1408GHz)|
|Sensitivity (5σ/1hr, point source)||2x10-18 Wm-2 (130 μm, 1st order), 5x10-18 (70 μm, 3rd order). Continuum: 100 mJy (1st order), 250 mJy (3rd order)||1.0-2.2x10-17 Wm-2 (high resolution), 40-88mJy (low resolution) [5 sigma/1 hr]||"A few" mK (Band 1a) to 100mK (Band 7b), 1 sigma/1hr|
|Resolution||900-2100 (1st order, 102-210 μm), 1800-3000 (2nd order, 72-98 μm), 2600-5400 (3rd order, 55-72 μm)||20-1000||1000-107|
For the latest information on instrument sensitivities please check the Herschel website at http://herschel.esac.esa.int/.
Note also that the PACS sensitivity below 57 microns is very low, although HSpot permits the entry of line observations at shorter wavelengths. | <urn:uuid:283f22b0-7910-4295-b33e-b1a48f778fb3> | 2.90625 | 779 | Knowledge Article | Science & Tech. | 68.827857 |
19th October 2008 - 01:23 PM
I have taken a more simplistic veiw on black holes. If you reach the speed of light you couldn't be seen. If we think about objects that perform this: electrons, electricity, radar. therefore if we look at an object in the very dense part of a galaxy. that has acheived enough mass that the spin at the event horizon is as fast the C. or has become energy it would appear lightless
27th October 2008 - 02:43 PM
I don't get what you are asking? Are you asking if a blackhole is made up of particles moving at light speed or if it is just a feild of energy drawing everything around it to itself?
28th October 2008 - 03:10 AM
Really depending on what you are actually referring to, we know photons constantly travel the speed of light even though losing energy when exiting gravitational fields. As far as black holes are concerned by devouring light, Its been said that can travel near speed of light. General Relativity states nothing exceeds speed of light so assuming light cant escape black holes and that's what many scientists theorize as Event Horizon, and Singularity. I'm not exactly sure at what you are getting at but mass-less particles adhere to light velocity, but larger masses and particles I don't believe travel light velocity. | <urn:uuid:2813e16e-c1a5-462f-88fd-126955c59523> | 2.84375 | 276 | Comment Section | Science & Tech. | 58.617 |
It would take as many human bodies to make up the sun as there are atoms in each of us. The geometric mean of the mass of a proton and the mass of the sun is 50 kilograms, within a factor of two of the mass of each person here.
Sir Martin Rees in a TED lecture. He suggests that humans have evolved to this scale, an almost beautiful mean between stars and atomic particles, because we must be large enough to permit massive complexity in structure while small enough to experience minimal gravitational effects.
It always makes me feel rather happy to think that everything had to be just so for our world, as we know it, to occur. Rees calls this quality of the universe its biophilia and describes it more here. | <urn:uuid:6c9022f0-8834-47e6-b256-e8106f451a07> | 2.734375 | 152 | Personal Blog | Science & Tech. | 51.584577 |
File:Global Warming Map.jpg
From Global Warming Art
This figure shows the difference in instrumentally determined surface temperatures between the period January 1999 through December 2008 and "normal" temperatures at the same locations, defined to be the average over the interval January 1940 to December 1980. The average increase on this graph is 0.48 °C, and the widespread temperature increases are considered to be an aspect of global warming.
This plot is based on the NASA GISS Surface Temperature Analysis (GISTEMP), which combines the 2001 GISS land station analysis data set (Hansen et al. 2001) with the Rayner/Reynolds oceanic sea surface temperature data set (Rayner 2000, Reynolds et al. 2002). The data itself was prepared through the GISTEMP online mapping tool, and the specific data set used is available here. This data was replotted in a Mollweide projection with a continuous and symmetric color scale. The smoothing radius is 1200 km, meaning that the reported temperature may depend on measurement stations located up to 1200 km away, if necessary.
This figure was prepared by Robert A. Rohde from public domain data.
- [abstract] [ [ Hansen, J., R. Ruedy, M. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. Peterson, and T. Karl (2001). "A closer look at United States and global surface temperature change". Journal of Geophysical Research 106: 23947-23963.
- Rayner, N. (2000). HadISST1 Sea ice and sea surface temperature files. Bracknell, U.K.: Hadley Center.
- Reynolds, R.W., N.A. Rayner, T.M. Smith, D.C. Stokes, and W. Wang (2002). "An improved in situ and satellite SST analysis for climate". J. Climate 15: 1609-1625.
GWArt images and pages linking to this file
Wikipedia pages and images linking to this file
Click on a date/time to view the file as it appeared at that time.
|current||03:28, 4 February 2009||800×596 (212 KB)||Robert A. Rohde|
|00:03, 18 November 2005||571×406 (77 KB)||Robert A. Rohde| | <urn:uuid:0ba00016-e8be-410d-965b-34f471e3f1bc> | 3.140625 | 493 | Knowledge Article | Science & Tech. | 66.882556 |
In Oracle PL/SQL, OPAQUE refers to the abstract data types whose internal representation are maintained by Oracle. The opaque type available in Oracle is XMLType. The XMLType data is stored as series of bytes and Oracle does not expose this internal representation. There are separate methods provided by Oracle to access the OPAQUE data.
A table named XMLTEST of XMLType is created. A XML document is inserted as a whole (as a CLOB), whose internal representation is not known.
SQL> CREATE TABLE XMLTEST OF XMLTYPE;
SQL> INSERT INTO XMLTEST values
1 row inserted.
FROM xmltest i,
EXTRACT(i.object_value, '/Business/Location/Service/Basics/Attribute[Name="id"]'))) s | <urn:uuid:fb88a9ab-a994-44ac-828c-bdf2198c060b> | 2.75 | 170 | Knowledge Article | Software Dev. | 38.0325 |
- Effects of nuclear orientation on fusion and fission in the reaction using 238U target nucleus (2010)
- Fission fragment mass distributions in the reaction of 30Si+238U were measured around the Coulomb barrier. At the above-barrier energies, the mass distribution showed a Gaussian shape. At the subbarrier energies, triple-humped distribution was observed, which consists of symmetric fission and asymmetric fission peaked at AL/AH ~ 90/178. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER) cross-sections for 30Si+238U. The cross-section for 263Sg at the abovebarrier energy agree with the statistical model calculation which assumes that the measured fission cross-section originates from fusion-fission, whereas the one for 264 Sg measured at the sub-barrier energy is smaller than the calculation, which suggests the presence of quasifission. | <urn:uuid:942d9a12-cd91-4a47-b7e2-96da24118788> | 2.875 | 204 | Academic Writing | Science & Tech. | 25.851094 |
The size and type of prey taken by adult rainbow bee-eaters in the south-west of Australia
*Subscription may be required
Bee-eaters are known to ‘… have an astonishingly narrow spectrum of [prey] preference, in effect, for most of them, only honeybees and social wasps’ (Fry 1984). Their predilection for honeybees (Apis spp.) has, in fact, led to conflict with apiarists (Lamothe 1979). However, they also are known to be opportunistic, exploiting transient foods (Fry 1984). The Rainbow Bee-eater Merops ornatus is no exception to these generalisations: Lea & Grey (1935) found hymenopteran remains in all the gizzards of 11 adult Rainbow Beeeaters they examined; Serventy & Whittell (1976) reported that hymenopterans comprised 63% of the 2753 head capsules retrieved from a single nest chamber excavated near Perth; and Calver et al. (1987) found that 95% of prey recovered from nest chambers on Rottnest Island, Western Australia, were hymenopterans. However, Rainbow Bee-eaters also have been observed feeding opportunistically on butterflies (Draffan et al. 1983), while Fry (1984) reported personal communications stating that moths, large flies, dragonflies and damselflies (odonatans) are fed to nestlings and that odonatans are the principal food for the young in Victoria. Barker & Vestjens (1989) also listed a wide range of arthropods and a single amphibian identified in the oesophagus or gizzard of Rainbow Bee-eaters but did not indicate the relative proportions of prey taken. Less is known of the preferred size range of prey for bee-eaters. Estimations have been made of the size of prey fed to nestlings (e.g. Hegner 1982 (Merops bullockoides), Krebs & Avery 1984 (Merops apiaster)), and Calver et al. (1987) determined the size of prey fed to nestling Rainbow Bee-eaters from measurements of prey remains. Helbig (1982, cited in Fry 1984) claimed that bee-eaters select prey of particular sizes and types, but we have been unable to locate data on the size of prey taken by adult Rainbow Bee-eaters in Australia. This paper reports data on the size of prey recovered from pellets regurgitated by adult Rainbow Bee-eaters at two widely separated sites in the south of Western Australia.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Biological Sciences and Biotechnology|
|Copyright:||(c) Birds Australia|
|Item Control Page| | <urn:uuid:58d94a25-b914-441f-bdac-a2468605746b> | 3.4375 | 579 | Academic Writing | Science & Tech. | 36.880587 |
A warm climate with CO2 levels similar to today delayed ice sheets from forming over land in the Arctic until less than 2 million years ago. That’s the latest instalment in a climate history scientists are building using sediment from a lake created by a giant meteorite impact around 3.6 million years ago. The international team has found that 3-3.2 million years ago, summer temperatures in the region were about 8°C warmer than they are today.
Julie Brigham-Grette from the University of Massachusetts, Amherst, explained that other scientists have estimated CO2 levels in the Pliocene period from 5.3 to 2.6 million years ago. “Though the estimates are quite broad, most scientists suggest that 2-3 million years ago CO2 levels may have been similar to today,” she told me. “Our data are consistent with that – the world today could be headed toward a Pliocene-like world.” And as well as pointing to the warmer future, these findings could also help unpick climate puzzles from our past.
These insights are the prize Julie and her team-mates sought on an epic trek to North-East Russia’s frozen wilderness in 2009. She was chief scientist for the US side of the team, leading the expedition alongside Martin Melles and Pavel Minyuk, chief scientists for the German and Russian sides. Their goal lay at the bottom of Lake El’gygytgyn, or Lake E. A 13 km wide crater blasted by a meteorite up to a kilometre in diameter that filled with water, Lake E has slowly collected sediment ever since. It’s unusual because it largely escaped damage from the creep of ice sheets, meaning scientists can use its sediment to rebuild conditions further back in time.
And to get there, Julie, Martin and Pavel had to pave political, financial, logistical, and actual physical paths, Julie explained. “This lake sits in an area that has no roads,” she said. “It was an amazing logistical feat to gather the drillers and equipment and get there, without damaging the environment. It was the most difficult scientific project I’ve ever undertaken.” Read the rest of this entry » | <urn:uuid:0345a0b9-b169-4e2d-86b3-06544233ba36> | 4.3125 | 462 | Personal Blog | Science & Tech. | 53.529208 |
Initially, I thought it was just a typo of iteration, as searching online for eteration yields no significant results.
But, then, I came across references that state that the term is coined by Crockford himself, in one of his talks.
Online, the only place where I could find an explanation is on his page, in The Factorial Tutorial, an article where, in Act 2, as a comment to a code sample, he states:
Act 2a: message iteration (eteration)
This seems to be part of a related pair of terms, as his next code sample, that performs recursion without using a stack, contains the other member of the pair:
Act 2b: message recursion (ecursion)
So, it seems that eteration and ecursion are terms invented and defined by Crockford himself to refer to message iteration and recursion in the context of the E Programming Language, designed on top of Java for developers who write distributed applications.
The fact that the language is called E is perhaps a reason to give its specific iteration and recursion flavors the chosen terminology (eteration and ecursion).
Eteration means to break a task into multiple turns so that on each
eteration, instead of going through a conventional loop, at the bottom
of the loop we call
setTimeOut, passing it a function which causes
us to do the next eteration. That means that the turns are going to be
short — the turn's only as long as one eteration – and we can do as
many eterations as we want and not lock up the event loop.
Check out the full talk in much better quality and accompanied by a full-text transcript here.
Also, for a reference on how such a technique might be implemented, consider the following scenario:
var feedbackDiv = document.getElementById("feedbackDiv");
feedbackDiv.innerHTML += "The Interface is Still Responsive!</br>";
var currentNumber = 0;
var loopStepDelay = 30;
var numbersDiv = document.getElementById("numbersDiv");
numbersDiv.innerHTML = currentNumber++;
<button onClick="testFeedback()">Try Me</button>
There are two
divs, one displaying the indices of the ongoing eteration, the other appending the text The Interface is Still Responsive! on each Try Me button press. As you can see from the code, the eteration steps are scheduled by
setTimeout some time interval apart, allowing for user interaction to take place and be processed as well. Thus, the eteration steps will continue to run as the user clicks on the button and triggers the update of the second div, maintaining the page's responsiveness while doing real progress with the work it has to perform (in this case, simply displaying indices). | <urn:uuid:86a81250-eb14-4b86-b072-19f24479ab59> | 3.171875 | 600 | Q&A Forum | Software Dev. | 35.709248 |
Pinning down the price of biodiversity
Conservation cost It would cost up to US$4.76 billion annually to protect the planet's threatened species from extinction, estimate researchers.
To establish and maintain protect areas, it would cost up to US$76 billion annually, they add.
An international team of scientists report their findings today in the journal Science.
"The total required [to protect biodiversity] is less than 20 per cent of annual global consumer spending on soft drinks," the researchers write.
Parties to the Convention on Biodiversity recently agreed to meet targets to preserve biodiversity by 2020.
Dr Stuart Butchart of BirdLife International and colleagues used data on birds to estimate the financial costs of meeting these targets.
They sampled 211 globally threatened bird species and asked experts to estimate the cost of preserving these from extinction.
The researchers then extrapolated this to the cost of protecting the 1115 globally threatened bird species and the cost of protecting all known threatened species globally.
"Threatened birds comprise 7.65 per cent of all threatened species on the global IUCN Red List suggesting that the total annual costs of conserving all 'known threatened species' ... may range from $3.41 billion ... to $4.76 billion," the researchers write.
The researchers also found it would cost US$76.1 billion annually to meet the target of managing and expanding protected areas to cover 17 per cent of terrestrial and in-land water areas (and 10 per cent of coastal and marine areas).
"Meeting these targets will require conservation funding to increase by at least an order of magnitude," write the researchers, but they add this is small compared to other expenditure.
Australian biodiversity expert Professor Hugh Possingham, from the University of Queensland agrees.
"We're talking about tiny sums of money," says Possingham, who was a reviewer of the study.
"For 20 per cent of Australia's defence budget we could not just secure all of Australia's threatened species, we could secure every threatened species on the planet."
He stresses that spending the money won't guarantee success, because multiple factors influence conservation outcomes.
"There'll still be some loss [of species] but it won't be catastrophic loss which is what we face at the moment."
Possingham says Australia is still underspending on nature conservation and this is responsible for a continued decline in species and landscape function.
"Our spending would have to go up about five to ten fold," he says.
Possingham says Australia has around 5 to 10 per cent of the world's biodiversity.
"Sadly we don't have 5 to 10 per cent of global GDP so we might need more help," he says. | <urn:uuid:1b7f34b3-1850-4a15-b1d3-903f0bbeb967> | 2.9375 | 552 | Truncated | Science & Tech. | 54.416805 |
What is a virus
pd1 at mole.bio.cam.ac.uk
Thu Jun 5 03:34:22 EST 2003
> Is a virus a living organism or a biological machine?
> Two Mechanical Engineers.
I don't think there's a definite answer to this: is a cell a biological
machine? There's also quite a large continuum of things that are
defined as viruses (obligate intracellular parasites with an eclipse
phase). My favourite virus (flu) has a relatively small genome with
only 10-11 genes and under the right circumstances it can limp along
without at least 4 of these. Quite simple diagrams can be drawn about
how the proteins encoded by these genes interact with each other to make
a new virus, as long as you're willing to ignore the host factors and
don't mind a degree of plausible guesswork. I've always thought of flu
as a piece of biological clockwork and have no problem with classifying
it as a non-living parasitic nanomachine. There are simpler viruses out
there too, even before you get down to the level of viroids and so on.
But, on the other hand, there are viruses with genomes that are orders
of magnitude larger than influenza's, including some that are comparable
in size to, if not larger than those of the smallest known free living
organisms. Where do you draw the line?
Probably not much help!
Paul (a virologist)
More information about the Virology | <urn:uuid:1721548f-6269-46dd-a4c4-4b6d30683ece> | 2.84375 | 316 | Comment Section | Science & Tech. | 53.716137 |
As the 25th leap second approaches (If you haven’t heard the news), there’s been a myriad of tweets and Facebook statuses joking about how to spend that extra moment when the clocks hit 11:59:60 UT. What many people don’t realize though is that a lot can happen in a second.
Let’s start with the basics. The SI definition of a second is 9,192,631,770 periods of the radiation produced by a particular transition in a cesium-133 atom. In the same second, this radiation (or any other form of light in a vacuum) would travel 299,792,458 meters, or approximately 7 times around the earth.
Speaking of light, our sun consumes around 500 billion kilograms of hydrogen every second to produce around 10^27 joules of energy. Although we receive only about a billionth of the total energy (10^18 joules), it’s still enough energy to power all of humanity for a year.
The amazing rate of natural events isn’t only in outer space. The earth experiences over 100 lightning strikes every second, amounting to more than 8.5 million strikes every day. The Amazon river discharges 175,000 cubic meters of water per second into the Atlantic, enough to fill seventy 10-lane Olympic swimming pools.
Finally, let’s not forget human accomplishments. I could not have written this post without help from Google, which is performing over 30000 searches every second. Sequoia, the IBM BlueGene supercomputer at Lawrence Livemore National Lab, can perform over 16 quadrillion operations (that’s 1.6 * 10^15!). However, even with these super computers, we can only simulate simple biological systems (ie: basic protein folding) for a few microseconds, much smaller than the actual time scale of cellular events. Each of the tens of trillions of cells in our body, for example, have proteins capable of replicating 50 nucleotides of DNA every second.
The things cited here barely scratch the surface of all the events happening every second of every day. It’s truly wonderful to appreciate everything that is going on around us without our knowing. I hope you enjoy the extra second and have a little new perspective whenever someone says “Seize the moment”.
****A word of caution to readers: Most of the values in this article, other than the exact definitions like the second or the speed of light, are meant to be order of magnitude approximations. You are likely to find different values if you use different sources. | <urn:uuid:5dde930d-5f34-416c-9d75-96f2eb790898> | 3.078125 | 539 | Personal Blog | Science & Tech. | 53.544503 |
CS 307: Debugging
Debugging programs is an important skill for a computer scientist.
Here are some hints about debugging:
- Document clearly what each function should do. Write a comment
(after a semicolon) that states what the function does.
Write a comment describing each argument, unless it is obvious.
Write a comment with an example of a call to the function.
; Compute the value of an investment of a fixed contribution for a
; given number of time periods at a specified interest rate.
; contribution = amount added at the end of a time period
; time = number of time periods
; interest = interest paid per time period, e.g. 6% = 0.06
; Example: (invest 1040 60 0.06) ; $1040 per year for 60 years at 6%
(define (invest contribution time interest) ...)
These comments are a specification of your program.
One source of bugs is an unclear (poorly understood, unwritten) specification.
Sometimes, a clear specification will make it obvious how to write the
program. One of the best ways to debug is not to write bugs; a good
- Test the function on an easy case first. Often, the easy case is
the base case of a recursive function. Make sure the answer is correct
for the easy case. Then try a slightly harder case -- one for which
you understand the answer.
> (invest 100 0 0.06)
> (invest 100 1 0.06)
> (invest 100 2 0.06)
Investing $100 zero times gives zero. Investing $100 at the end of one time
period leaves us with the given $100. Investing $100 for two time periods
gives us interest of $6 on $100 during the second time period.
If your function works on the base case and a few more cases, it probably
works for all cases; if not, it will be easier to understand and fix the
function when the case is an easy one.
- Trace your functions. Use (trace fn ) to
trace the function fn. You can turn off a trace with
The trace will show the arguments of a function on entry and the result on
exit. The entry and exit are matched by vertical alignment of the trace
- As soon as you see a bug, track it down and fix it.
Develop a keen eye for anything that looks unusual in your output; if
you see something abnormal, focus on it.
- Test your functions one at a time.
This is easy in Lisp: simply type in a call to a function
with test arguments, even if it is not the ``main'' function.
It is easy to test a single function in isolation, but hard to test a
- Use rapid prototyping and evolve your programs:
write a program that does part of the job, test it, then expand it.
When you get part of the program working, you can expand
on that model; this is better than repeating the same mistake many times
in your code before doing any testing.
- If your program ``cannot possibly be doing what it is doing'',
the bug is probably something that you are not looking at. Take a wider
view and look at other things.
- Instrument your code with debugging printouts: print out internal values
and look for abnormalities. Sometimes students stay up all night trying
to reason about why their program does not work, when a simple printout
would make the problem obvious.
You can detect internal errors and stop your program (and then get variable
values) using an (error "message") call.
(error "The elusive bug has occurred!"))
- When you get an error break, DrScheme can provide additional information:
- Click the function name to get instant documentation of the
function in which the error occurred.
- Click the Bug symbol to get backtrace information.
This will show the sequence of calls that reached the error and | <urn:uuid:dfd726a1-b68d-4c44-bec5-3076363704e5> | 3.5625 | 844 | Tutorial | Software Dev. | 64.189432 |
Pattern Maching in Programming Languages
Several functional programming languages (e.g. Scala, Haskell, and ML) support pattern matching of data objects. Recently Martin Odersky, the designer of Scala, explained pattern matching.
In a recent interview with Bill Venners at Artima.com Martin Odersky explained how pattern matching works in Scala, and what its role is.
It is impossible to argue that pattern matching isn't useful to programmers. Especially to those writing compilers. But I don't agree as Martin says, that it is essential. I think he realizes this, and it was just a mild exageration. In the world of compiler writing, after you have gotten used to pattern matching, it is very painful to go back.
I do however have one issue with pattern matching: the deconstruction of objects is coupled with the construction of the object. I don't believe that the consumer of data (e.g. objects) should care about how that data is produced or structured. Otherwise, we can't make changes to the production of the objects, without affecting the consumption. In other words: these concerns are coupled.
So what should a language designer do?
Well I am thinking that maybe we can have pattern matching, and decouple it from object construction and data layout by having objects expose a single function which returns a tuple representing the data layout to be matched on.
So for example in an XML tree, an XML node might have a function with the signature "deconstruct() : List<XMLNode>" which could be used in pattern matching statements.
This way the actual layout of data in the XML node class, won't affect pattern matching. We are minimizing the point of contact between the pattern matching and the class.
The only other idea I have is introducing a type switch statement into the langauge. This would allow programmers to replace:
if (x is A)
f(x as A);
else if (x is B)
g(g as B);
With the following code
case (A) :
case (B) :
Arguably this is a poor man's pattern matching, but maybe it is still an improvement over nothing, even if it isn't as powerful as Scala pattern matching. | <urn:uuid:5a68a49d-5180-4370-a6a8-189973105fec> | 3.078125 | 468 | Personal Blog | Software Dev. | 58.497976 |
Climate Number: 28 Cubic Miles
Each year the United States pumps about 28 cubic miles of water out its groundwater aquifers – natural underground storage areas – for irrigation, drinking water, industrial purposes, etc. While about 84.6 percent of these withdrawals are recharged to the aquifers through natural recharge (primarily rainfall) or artificial recharge (recharge to the groundwater from human activities), 15.4 percent, or about 4.25 cubic miles, of America’s groundwater withdrawals flow into the oceans without being returned as rainfall. Globally, about 34 cubic miles of groundwater is lost to the oceans every year. While groundwater losses can be replenished over time, losses from arid or semi-arid regions may take thousands of years to recover. Much of the groundwater being pumped from underneath the Great Plains region, for example, is fossil groundwater that was deposited by the melting North American Ice Sheet over 10,000 years ago.
For comparison: The 34 cubic miles of groundwater sent to the oceans raises global sea levels by 0.39 millimeters each year, which is a significant fraction of the total 2.1 millimeter annual sea-level rise. Sea level rise from the water coming off the shrinking Greenland and Antarctic Ice Sheets is about 1.3 millimeters per year.
Source: Church, JA et al. “Revisiting the Earth’s sea-level and energy budgets from 1961 to 2008.” Geophysical Research Letters 38 (2011): L18601. | <urn:uuid:4c601af6-a61a-4c6c-ad8c-81aaa5fff3ff> | 3.6875 | 308 | Knowledge Article | Science & Tech. | 50.990625 |
5 List handling
Lists can only be built starting from the end and attaching list elements at the beginning. If you use the ++ operator like this
List1 ++ List2
you will create a new list which is copy of the elements in List1, followed by List2. Looking at how lists:append/1 or ++ would be implemented in plain Erlang, it can be seen clearly that the first list is copied:
append([H|T], Tail) -> [H|append(T, Tail)]; append(, Tail) -> Tail.
So the important thing when recursing and building a list is to make sure that you attach the new elements to the beginning of the list, so that you build a list, and not hundreds or thousands of copies of the growing result list.
Let us first look at how it should not be done:
bad_fib(N) -> bad_fib(N, 0, 1, ). bad_fib(0, _Current, _Next, Fibs) -> Fibs; bad_fib(N, Current, Next, Fibs) -> bad_fib(N - 1, Next, Current + Next, Fibs ++ [Current]).
Here we are not a building a list; in each iteration step we create a new list that is one element longer than the new previous list.
To avoid copying the result in each iteration, we must build the list in reverse order and reverse the list when we are done:
tail_recursive_fib(N) -> tail_recursive_fib(N, 0, 1, ). tail_recursive_fib(0, _Current, _Next, Fibs) -> lists:reverse(Fibs); tail_recursive_fib(N, Current, Next, Fibs) -> tail_recursive_fib(N - 1, Next, Current + Next, [Current|Fibs]).
Lists comprehensions still have a reputation for being slow. They used to be implemented using funs, which used to be slow.
In recent Erlang/OTP releases (including R12B), a list comprehension
[Expr(E) || E <- List]
is basically translated to a local function
'lc^0'([E|Tail], Expr) -> [Expr(E)|'lc^0'(Tail, Expr)]; 'lc^0'(, _Expr) -> .
In R12B, if the result of the list comprehension will obviously not be used, a list will not be constructed. For instance, in this code
[io:put_chars(E) || E <- List], ok.
or in this code
. . . case Var of ... -> [io:put_chars(E) || E <- List]; ... -> end, some_function(...), . . .
the value is neither assigned to a variable, nor passed to another function, nor returned, so there is no need to construct a list and the compiler will simplify the code for the list comprehension to
'lc^0'([E|Tail], Expr) -> Expr(E), 'lc^0'(Tail, Expr); 'lc^0'(, _Expr) -> .
lists:flatten/1 builds an entirely new list. Therefore, it is expensive, and even more expensive than the ++ (which copies its left argument, but not its right argument).
In the following situations, you can easily avoid calling lists:flatten/1:
- When sending data to a port. Ports understand deep lists so there is no reason to flatten the list before sending it to the port.
- When calling BIFs that accept deep lists, such as list_to_binary/1 or iolist_to_binary/1.
- When you know that your list is only one level deep, you can can use lists:append/1.
... port_command(Port, DeepList) ...
... port_command(Port, lists:flatten(DeepList)) ...
A common way to send a zero-terminated string to a port is the following:
... TerminatedStr = String ++ , % String="foo" => [$f, $o, $o, 0] port_command(Port, TerminatedStr) ...
Instead do like this:
... TerminatedStr = [String, 0], % String="foo" => [[$f, $o, $o], 0] port_command(Port, TerminatedStr) ...
> lists:append([, , ]). [1,2,3] >
> lists:flatten([, , ]). [1,2,3] >
In the performance myth chapter, the following myth was exposed: Tail-recursive functions are MUCH faster than recursive functions.
To summarize, in R12B there is usually not much difference between a body-recursive list function and tail-recursive function that reverses the list at the end. Therefore, concentrate on writing beautiful code and forget about the performance of your list functions. In the time-critical parts of your code (and only there), measure before rewriting your code.
Important note: This section talks about lists functions that construct lists. A tail-recursive function that does not construct a list runs in constant space, while the corresponding body-recursive function uses stack space proportional to the length of the list. For instance, a function that sums a list of integers, should not be written like this
recursive_sum([H|T]) -> H+recursive_sum(T); recursive_sum() -> 0.
but like this
sum(L) -> sum(L, 0). sum([H|T], Sum) -> sum(T, Sum + H); sum(, Sum) -> Sum. | <urn:uuid:fd8bceb1-b3c9-4059-8397-ec3bafebe778> | 3.5625 | 1,250 | Documentation | Software Dev. | 73.357873 |
Facts about Roentgenium
Facts about Roentgenium - Element included on the Periodic Table
Facts about the Definition of the Element Roentgenium
The Element Roentgenium is defined as...
Roentgenium is a chemical element in the periodic table that has the symbol Rg (formerly temporarily Uuu) and atomic number 111. It has an atomic weight of 272 making it one of the super-heavy atoms. It is a synthetic element whose only known isotope has a half-life of around 15 ms before it decays into meitnerium. Due to its presence in Group 11 it is a transition metal and so probably metallic and solid.
Interesting Facts about the Origin and Meaning of the element name Roentgenium
What are the origins of the word Roentgenium ?
The name was given in honour of honour of Wilhelm Roentgen.
Facts about the Classification of the Element Roentgenium
Roentgenium is classified as a "Transition Metal" which are located in Groups 3 - 12 of the Periodic Table. An Element classified as a Transition Metals is ductile, malleable, and able to conduct electricity and heat.
Brief Facts about the Discovery and History of the Element Roentgenium
Roentgenium was discovered by S. Hofmann at the Gesellschaft fur Schwerionenforschung in Darmstadt, Germany in 1994.
Occurrence of the element Roentgenium in the Atmosphere
Common Uses of Roentgenium
No known use
The Properties of the Element Roentgenium
Name of Element : Roentgenium
Symbol of Element : Rg
Atomic Number of Roentgenium : 111
Atomic Mass: amu
Melting Point: N/A
Boiling Point: N/A
Number of Protons/Electrons in Roentgenium : Unknown
Number of Neutrons in Roentgenium : Unknown
Crystal Structure: Unknown
Color of Roentgenium : Unknown
The element Roentgenium and the Periodic Table
Find out more facts about Roentgenium on the Periodic Table which arranges every chemical element according to its atomic number, as based on the periodic law, so that chemical elements with similar properties are in the same column. Our Periodic Table is simple to use - just click on the symbol for Roentgenium for additional facts and info and for an instant comparison of the Atomic Weight, Melting Point, Boiling Point and Mass - G/cc of Roentgenium with any other element. An invaluable source for more interesting facts and information about the Roentgenium element and as a Chemistry reference guide.
Facts and Info about the element Roentgenium - IUPAC and the Modern Standardised Periodic Table
The Standardised Periodic Table in use today was agreed by the International Union of Pure Applied Chemistry, IUPAC, in 1985 which includes the Roentgenium element. The famous Russian Scientist, Dimitri Mendeleev, perceived the correct classification method of "the periodic table" for the 65 elements which were known in his time. Roentgenium was discovered by S. Hofmann at the Gesellschaft fur Schwerionenforschung in Darmstadt, Germany in 1994. The Standardised Periodic Table now recognises more periods and elements than Dimitri Mendeleev knew in his day but still all fitting into his concept of the "Periodic Table" in which Roentgenium is just one element that can be found.
Facts and Info about the Element Roentgenium
Information Facts about the Roentgenium Element | <urn:uuid:dcd0c033-6d19-4331-8532-94770c55b9ec> | 3.765625 | 774 | Knowledge Article | Science & Tech. | 28.727345 |
Actinopterygii (ray-finned fishes) > Perciformes
(Perch-likes) > Zoarcidae
(Eelpouts) > Lycodinae
Etymology: Lycodes: Greek, lykos = wolf + Greek, suffix, oides = similar to (Ref. 45335).
Environment / Climate / Range
Marine; demersal; depth range 19 - 1750 m (Ref. 58426). Polar; -1°C - ? (Ref. 4695); 83°N - 41°N
Size / Weight / Age
Maturity: Lm ? range ? - ? cm
Max length : 26.0 cm TL male/unsexed; (Ref. 4695); common length : 18.0 cm TL male/unsexed; (Ref. 4695)
Morphology | Morphometrics
Vertebrae: 90 - 93. Pelvic fins small (Ref. 4695). Young with pale, yellowish-brown body, with 6-8 light and narrow cross bands which are more distinct on the dorsal fin; larger individuals lose the bands, becoming more or less uniformly colored (Ref. 4695).
Circumarctic (Ref. 11954). Northeast Atlantic: northeast Greenland, Jan Mayen Island, northern coasts of Iceland, Faroes-Shetland slope, northern part of Barents Sea, White Sea and around Spitsbergen. Northwest Atlantic: Arctic Canada to Labrador and Gulf of St. Lawrence; possibly to Cape Cod in Massachusetts, USA (Ref. 7251). Arctic Ocean: Kara Sea, western part of Laptev Sea, Beaufort Sea and Arctic Canada. Subspecies(?) Lycodes pallidus marisalbi in White Sea only (Ref. 4695).
Found on muddy bottoms (Ref. 4695). Benthic (Ref. 58426). Feeds mostly on endobenthic prey such as small bivalves, polychaetes and small crustaceans in addition to detritus. It seems to get the bulk of its food by burrowing in the sediment (Ref. 13532). Ripe females recorded in September in the Kara Sea (Ref. 4695). Minimum depth from Ref. 58018.
Anderson, M.E., 1994. Systematics and osteology of the Zoarcidae (Teleostei: Perciformes). Ichthyol. Bull. J.L.B. Smith Inst. Ichthyol. 60:120 p.
IUCN Red List Status (Ref. 90363)
Threat to humans
ReferencesAquacultureAquaculture profileStrainsGeneticsAllele frequenciesHeritabilityDiseasesProcessingMass conversion
CollaboratorsPicturesStamps, CoinsSoundsCiguateraSpeedSwim. typeGill areaOtolithsBrainsVision
Estimates of some properties based on empirical models
Phylogenetic diversity index (Ref. 82805
= 0.5000 [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00139 (-0.18389 - 0.18667), b=3.15 (3.04 - 3.26), based on LWR estimates for this family-BS (Ref. 93245
Trophic Level (Ref. 69278
): 3.3 ±0.3 se; Based on diet studies.
Resilience (Ref. 69278
): Medium, minimum population doubling time 1.4 - 4.4 years (Preliminary K or Fecundity.).
Vulnerability (Ref. 59153
): Moderate vulnerability (35 of 100) . | <urn:uuid:dbb4f4ad-f95b-4a7e-8483-80ef3430efc4> | 2.765625 | 782 | Knowledge Article | Science & Tech. | 64.406838 |
Peter G. Brewer and Edward T. Peltzer
Monterey Bay Aquarium Research Institute
Franklyn M. Orr, Jr
This paper was prepared for presentation at the 2001 SPE Annual Technical Conference and Exhibition held in New Orleans, LA, Sept. 30-Oct. 3, 2001.
Substantial progress has been made in carrying out small-scale field experiments to investigate the scientific basis for disposal of CO2 that results from burning of fossil fuels in the deep ocean. A remotely operated vehicle (ROV) was used to carry liter quantities of CO2 to depths from 250 to 3650 m in the ocean and to release the CO2 in a controlled manner. A video imaging system allowed observation of the behavior of the CO2 released. CO2 released at intermediate depths forms bubbles that rise. Below about 2750 m liquid CO2 is more dense than sea water, and CO2 released at greater depths descends further. Hydrate formation was observed for depths below about 350 m. We show through video imagery, direct measurement, and model calculations that the dissolution rate of liquid CO2 in the deep ocean is 3 μmoles/cm²/sec. The slow dissolution rate limits the local concentration of CO2. Limited observations of the approach of marine life to CO2 released on the sea floor showed no apparent avoidance reactions.
© 1999 Society of Petroleum Engineers Inc.
This work was supported by the David and Lucile Packard Foundation through a grant to the Monterey Bay Aquarium Research Institute. The authors are deeply indebted to the officers and crews of the R/V Point Lobos and the R/V Western Flyer, the pilots of the ROV Ventana and the ROV Tiburon, and the MBARI Operations group for their skilled technical support. | <urn:uuid:d17fd370-f83f-4491-a9b4-bb8ac65fcfde> | 3.359375 | 361 | Academic Writing | Science & Tech. | 52.933333 |
Tiny plant-like organisms called zooxanthella live in the tissues of many animals, including some corals, anemones, and jellyfish, sponges, flatworms, mollusks and foraminifera. These microscopic algae capture sunlight and convert it into energy, just like plants, to provide essential nutrients to the corals. In exchange, they have a place to live inside the animal's body. But when the zooxanthellae are under stress, such as high temperatures, they will die or leave their host—a process known as bleaching.
Close-up of a Coral Polyp
What Is Coral? A Coral Polyp and Zooxanthellae
Bleached Corals, Pacific Ocean
Share your comments here.
* When you click submit, your comment will be added to the queue for review and will be published after approval. | <urn:uuid:fcc585e4-96a0-44df-bc8a-2a25896eae4c> | 4.0625 | 183 | Knowledge Article | Science & Tech. | 37.974508 |
|Aug11-09, 10:21 PM||#1|
Thermal Physics - Dalton's Law etc
Inside the leaf of a plant, water vapour passes from the liquid phase to the vapour phase at the walls of the mesophyll cells, as shown in the figure (N/A due to copyright). The water vapour then diffuses through the intercellular air spaces and eventually exits the leaf through the stomatal pores. The diffusion constant for water vapor in air is D = 2.4 x 10−5 m2s−1. A stomatal pore has a cross-sectional area A = 6.8 x 10−11 m2 and a length L = 7.0 x 10−5 m. The plant is being propagated in a controlled environment: T = 17 °C, relative humidity 61 %. The saturated vapour pressure of water at 17 °C is 1.93 kPa.
(a) Assuming that the air around the plant is an ideal gas, what is the concentration of water molecules per cubic meter in the air? __________ molecules/m³
(b) Given that the molar mass of water is 18.0 g mol−1, what is the concentration of water in the air in kg/m³? __________ kg/m³
2. Relevant equations - don't know...
I know that the partial pressure of water vapour is 1.18kPa which can be worked out by using the saturated vapour pressure of water and the relative humidity ( x/1.93 = 0.61 , x = 1.18kPa )
But what do you do with it? I think its got something to do with the total pressure and etc but don't know exactly how
Please help me
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|Dalton's Law of Partial Pressures||Introductory Physics Homework||0| | <urn:uuid:58df235f-09f6-46c4-8119-bd5d30b783ac> | 3.078125 | 485 | Comment Section | Science & Tech. | 81.206667 |
July 20, 2012 | 2
The French–Italian Concordia research station in Antarctica is not your typical location for a medical practice, but working there has its perks. Physician Alexander Kumar and Erick Bondoux, two residents passing austral winter at Concordia, snapped this photo of the dramatic aurorae over the station on July 18.
The outpost is so isolated that no one can come or go for months during the winter, during which time the 13 people there experience complete darkness for more than 100 consecutive days. Add to that an elevation of roughly 3,200 meters, and the conditions at Concordia station are, in a word, harsh.
Enter Kumar, who, as a human spaceflight research M.D. for the European Space Agency, is charged with investigating "how far human physiology and psychology can be pushed towards a future manned mission to Mars," according to his Web site.
In the meantime he and his crew members do get to enjoy the almost otherworldly aurora australis, or southern lights. Aurorae over Earth's poles are the product of charged particles streaming from the sun and colliding with atoms and molecules in the upper atmosphere. At most latitudes the planet's magnetic field repels those particles, but the thinner shielding over the poles allows protons and electrons to penetrate more deeply. The green glow photographed by Kumar and Bondoux emanates from oxygen atoms in the atmosphere returning to their lowest-energy state after being excited by charged solar particles.
Deadline: Jun 30 2013
Reward: $1,000,000 USD
This is a Reduction-to-Practice Challenge that requires written documentation and&
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The Seeker for this Challenge desires proposals for chemical methods that could rapidly degrade a dilute aqueous solution
Save 66% off the cover price and get a free gift!
Learn More >>X | <urn:uuid:5558b341-af85-43a6-8154-4b01201dddc9> | 2.78125 | 393 | Truncated | Science & Tech. | 37.84707 |
Data reported by the weather station: 865650
Latitude: -34.48 | Longitude: -54.3 | Altitude: 18
|Main||Year 1983 climate||Select a month|
To calculate annual averages, we analyzed data of 360 days (98.63% of year).
If in the average or annual total of some data is missing information of 10 or more days, this is not displayed.
The total rainfall value 0 (zero) may indicate that there has been no such measurement and / or the weather station does not broadcast.
|Annual average temperature:||15.9°C||360|
|Annual average maximum temperature:||21.8°C||360|
|Annual average minimum temperature:||11.5°C||360|
|Annual average humidity:||80.8%||360|
|Annual total precipitation:||1242.56 mm||359|
|Annual average visibility:||12.7 Km||360|
|Annual average wind speed:||11.6 km/h||360|
Number of days with extraordinary phenomena.
|Total days with rain:||98|
|Total days with snow:||0|
|Total days with thunderstorm:||32|
|Total days with fog:||51|
|Total days with tornado or funnel cloud:||0|
|Total days with hail:||0|
Days of extreme historical values in 1983
The highest temperature recorded was 34°C on February 10.
The lowest temperature recorded was -1.6°C on June 30.
The maximum wind speed recorded was 83.2 km/h on October 17. | <urn:uuid:b5fce022-7a0d-4eb5-8636-4c32b22598ce> | 2.71875 | 357 | Structured Data | Science & Tech. | 72.329555 |
Death of small stars
In a low mass star in its last stage, with a helium burning shell, stellar modelling suggests that the helium burning shell becomes unstable, and
burns in bursts. This causes the star to eject much of its outer layers.
The result is a ``planetary nebula'' which may last for 50,000 years before
it dissapates into space.
Here is some evidence. (Colors in general aren't exactly real in these
Left behind in the middle is a white dwarf star.
- The Egg Nebula,
where this process seems to be going on now. It appears that light gets
out near the poles of the star and is reflected from dust.
- NGC7027. The outer layers
appear to have been ejected in a spherically symmetric fashion; the inner
layers are more disorganized.
- MyCn18, The Hourglass Nebula
- NGC6543, the Cat's Eye Nebula,
a quite complex planetary nebula, possibly associated with a dying member of
a binary system.
Type Ia supernovae
There are observed very violent explosions called supernovae. It
appears that one kind of supernova is induced when extra mass from
a companion star falls onto a white dwarf. The carbon core gets
hot enough to begin fusion reactions, and does so explosively. It
is like a huge nuclear bomb.
Davison E. Soper, Institute of Theoretical Science,
University of Oregon, Eugene OR 97403 USA | <urn:uuid:27444902-b000-4f44-a088-d06f57b23227> | 3.296875 | 322 | Academic Writing | Science & Tech. | 52.866 |
More specifically, an ampersand (&) prepended to an argument name means that the argument will be passed by reference (http://www.php.net/manual/en/language.references.pass.php).
How to read a function definition (prototype)
Each function in the manual is documented for quick reference. Knowing how to read and understand the text will make learning PHP much easier. Rather than relying on examples or cut/paste, everyone should know how to read function definitions (prototypes). Let's begin:
Note: Prerequisite: Basic understanding of types
Although PHP is a loosely typed language, it's important to have a basic understanding of types as they have important meaning.
strlen (PHP 4, PHP 5) strlen -- Get string length Description int strlen ( string $string ) Returns the length of given string.
|strlen||The function name.|
|(PHP 4, PHP 5)||strlen() has been around in all versions of PHP 4 and PHP 5|
|int||Type of value this function returns, which is an integer (i.e. the length of a string is measured in numbers).|
|( string $string )||The first (and in this case the only) parameter/argument for this function is named string, and it's a string.|
We could rewrite the above function definition in a generic way:
returned type function name ( parameter type parameter name )
Many functions take on multiple parameters, such as in_array(). Its prototype is as follows:
bool in_array ( mixed $needle, array $haystack [, bool $strict])
What does this mean? in_array() returns a boolean value, TRUE on success (if the needle was found in the haystack) or FALSE on failure (if the needle was not found in the haystack). The first parameter is named needle and it can be of many different types, so we call it "mixed". This mixed needle (what we're looking for) can be either a scalar value (string, integer, or float), or an array. haystack (the array we're searching in) is the second parameter. The third optional parameter is named strict. All optional parameters are seen in [ brackets ]. The manual states that the strict parameter defaults to boolean FALSE. See the manual page on each function for details on how they work.
There are also functions with more complex PHP version information. Take html_entity_decode() as an example:
(PHP 4 >= 4.3.0, PHP 5)
This means that this function has only been available in a released version since PHP 4.3.0. | <urn:uuid:cb0333e8-36c2-4aac-8ba6-9dc7970b49bf> | 3.625 | 565 | Documentation | Software Dev. | 63.52892 |
Brief Overview of Inertial-Electrostatic-Confinement Fusion
John F. Santarius
Fusion Technology Institute
Historically, most fusion research has focused on energy production in two basic configurations: magnetic confinement (magnetic fusion energy or MFE), and inertial confinement (inertial fusion energy or IFE). Each of these may lead eventually to a viable fusion reactor, yet they tend to be large, complicated, and expensive. This generates many physics and engineering difficulties, so the time frame for their development remains uncertain.
The present note describes a fundamentally different fusion concept based on electrostatic focusing of ions into a dense core. Generically, such systems are called inertial-electrostatic confinement (IEC) fusion systems. In the 1950's, research was done on one form of IEC, purely electrostatic confinement, in which a voltage difference on concentric grids focuses charged particles . Ions accelerate down the electrostatic potential in spherical geometry, and convergence at the origin gives high density . Figure 1 shows the basic geometry, and the key physics elements appear in Figure 2. Another purely electrostatic approach is to inject a sufficiently high electron current into a magnetic trap to form a virtual cathode, which then traps a high density of ions in the resulting electrostatic potential well . This approach must find an operating regime that reduces transverse momentum and instabilities to a level allowing sufficient focusing for fusion power production. A third approach utilizes a Penning Trap to confine the electrons
Figure 1: Grids plus energetic
plasma core of the simplest IEC configuration.
Figure 2: Electrostatic potential and ion density radial profiles in an IEC device .
The gridded IEC approach possesses the significant advantage that ions can be accelerated to high voltages (tens of keV) with relative ease. Even small IEC devices appear able to produce high-energy (MeV) neutrons and protons or electromagnetic radiation at levels useful for medical, environmental, and industrial applications. This should greatly facilitate IEC fusion development. Examples of applications that University of Wisconsin personnel have begun investigating include [4-6]:
Inertial-electrostatic confinement devices possess another key feature: they are excellent configurations for burning the second-generation advanced fusion fuels D3He, and potentially could even burn the third-generation fuels, 3He-3He and p-11. Possible applications include not only electricity production, but also high-energy (~15 MeV) proton production for positron production and other uses. In IEC devices, the main energy losses should be due to transport of electrons or ions (direct loss of fusion products) and to bremsstrahlung radiation.
An important aspect of the IEC concept is that much of the relevant physics can be tested in moderately sized experiments, and the University of Wisconsin [7-9], among others [10, 11], presently conducts such research. A small, purely electrostatic-confinement experiment with spherical grids accelerating the ions, is being used at UW to investigate core convergence and optimize production of neutrons and protons.
Recently, a concept called the Polywell was invented . Its operating principle is magnetic confinement of electrons and electrostatic confinement of ions in a geometry of nearly spherical symmetry. The basic physics of the Polywelltm is illustrated in Fig. 3. The magnetic-field cusps (only two of many symmetrically located cusps are shown) are formed by currents flowing in conductors placed at the edges of various polyhedral configurations.
Figure 3: Physics concepts for the Polywelltm concept .Injected electrons form a cloud throughout the interior of the sphere, resulting in a negative electrostatic potential well, as shown in Fig. 3. Ions are injected at low energy or created by neutral gas ionization at the outer edge of the electron cloud. These ions fall down the potential hill and converge on the origin of the sphere, giving a small, spherical core of high density (see Fig. 2). For a sufficiently deep potential well, steady-state fusion power can be generated in this core. Preliminary investigations of the Polywelltm concept have led to the conclusion that it can be a viable fusion reactor [2, 12-14], although several questions remain [15, 16].
In the Penning trap approach , combined electric and magnetic fields confine electrons, which create the electrostatic potential well required to accelerate ions into a dense core. The basic concept appears in Figure 4. The possibility of achieving high core density using radio-frequency waves at the edge to create radial plasma oscillations is under investigation .
Figure 4: Basic configuration of a Penning-trap IEC device.
Polywelltm reactors are intrinsically steady-state, driven devices, and the main energy-loss mechanism should be electron transport out the cusps. This mechanism, however, is expected to be fundamentally different from the loss of electrons out of magnetic-mirror or multipole cusps , because the Polywelltm will operate at b~1 (b?plasma pressure/magnetic-field pressure). This is predicted to greatly reduce plasma transport losses in cusp geometry .
Both the physics and engineering of IEC fusion reactors would be profoundly different from that of either magnetic or inertial fusion reactors. Because fusion-product energies are much higher than the electrostatic potential well depth, fusion products are not confined and fusion ash does not accumulate. An intriguing possibility for IEC reactors is converting much of the energy of the escaping fusion products directly to electricity using spherically symmetric grids of constant voltage, as shown in Figure 5.
Figure 5: An IEC reactor configured for direct electrostatic conversion of fusion-product energy to electricity .
Key physics and engineering issues that remain to be resolved for inertial-electrostatic-confinement fusion devices are:
If these issues get resolved favorably, the engineering of IEC reactors appears manageable, and IEC reactors should be very attractive with regard to safety, environment, and economics. Even if the realization of economic electricity production takes considerable development time, near-term IEC devices appear able to produce levels of high-energy neutrons and protons that have useful industrial and medical applications.
1. R. Hirsch, "Inertial-Electrostatic Confinement of Ionized Fusion Gases," Journal of Applied Physics 38, 4522 (1967).
2. R.W. Bussard, "Some Physics Considerations of Magnetic Inertial-Electrostatic Confinement: A New Concept for Spherical Converging-flow Fusion," Fusion Technology 19, 273 (1991).
3. D.C. Barnes, R.A. Nebel, and L. Turner, "Production and Application of Dense Penning Trap Plasmas," Physics of Fluids B 5, 3651 (1993).
4. G.L. Kulcinski, "Near Term Commercial Opportunities from Long Range Fusion Research," Fusion Technology 30, 411 (1996).
5. G.L. Kulcinski and J.F. Santarius, "Reducing the Barriers to Fusion Electric Power," Journal of Fusion Energy 17, 17 (1997).
6. G.L. Kulcinski, "Non-Electric Applications of Fusion Energy--An Important Precursor to Commercial Electric Power," Fusion Technology, Part 2 34, 477 (1998).
7. T.A. Thorson, R.D. Durst, R.J. Fonck, and L.P. Wainwright, "Convergence, Electrostatic potential, and desity measurements in a spherically convergent ion focus," Physics of Plasmas 4, 4 (1997).
8. R.P. Ashley, G.L. Kulcinski, J.F. Santarius, S.K. Murali, and G. Piefer, "D-3He Fusion in an Inertial Electrostatic Confinement Device," 18th IEEE Symposium on Fusion Engineering (IEEE, Albuquerque, New Mexico, 1999), p. 37.
9. R.P. Ashley, G.L. Kulcinski, J.F. Santarius, S.K. Murali, G. Piefer, et al., "Steady-State D-3He Proton Production in an IEC Fusion Device," Fusion Technology, Part 2 39, 546 (2001).
10. G.H. Miley, J. DeMora, J. Stubbers, I.V. Tzonev, R.A. Anderl, et al., "Optimization of IEC Grid Design for Maximum Neutron Production," Fusion Technology 30, 1315 (1996).
11. D.C. Barnes, T.B. Mitchell, and M.M. Schauer, "Beyond the Brillouin Limit with the Penning Fusion Experiment," Physics of Plasmas 4, 1745 (1997).
12. N.A. Krall, "The Polywell: A Sperically Convergent Ion Focus Concept," Fusion Technology 22, 42 (1992).
13. M. Rosenberg and N.A. Krall, "The effect of collisions in maintaining a non-Maxwellian plasma distribution in a spherically convergent ion focus," Phys. Fluids B 4, 1788 (1992).14. S.K. Wong and N.A. Krall, "Potential well formation by injection of electrons with various energy distributions into a sphere or a slab," Physics of Fluids B 4, 4140 (1992).
15. W.M. Nevins, "Can Inertial Electrostatic Confinement Work Beyond the Ion-Ion Collisional Time Scale?," Physics of Plasmas 2, 3804 (1995).
16. T.H. Rider, "A general critique of inertial-electrostatic confinement fusion systems," Physics of Plasmas 2, 1853 (1995).
17. R.A. Nebel and D.C. Barnes, "The Periodically Oscillating Plasma
Sphere, Fusion Technology 34, 28 (1998) | <urn:uuid:991b2f30-a69c-483f-8157-834f38e53e6a> | 3.515625 | 2,095 | Academic Writing | Science & Tech. | 45.146494 |
[This documentation is for preview only, and is subject to change in later releases. Blank topics are included as placeholders.]
Gets or sets the text trimming behavior to employ when content overflows the content area.
Assembly: PresentationFramework (in PresentationFramework.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
This example demonstrates the usage and effects of the values available in the TextTrimming enumeration.
The following example defines a TextBlock element with the attribute set.
<TextBlock Name="myTextBlock" Margin="20" Background="LightGoldenrodYellow" TextTrimming="WordEllipsis" TextWrapping="NoWrap" FontSize="14" > One<LineBreak/> two two<LineBreak/> Three Three Three<LineBreak/> four four four four<LineBreak/> Five Five Five Five Five<LineBreak/> six six six six six six<LineBreak/> Seven Seven Seven Seven Seven Seven Seven </TextBlock>
Setting the corresponding TextTrimming property in code is demonstrated below.
There are currently three options for trimming text: CharacterEllipsis, WordEllipsis, and None.
When is set to CharacterEllipsis, text is trimmed and continued with an ellipsis at the character closest to the trimming edge. This setting tends to trim text to fit more closely to the trimming boundary, but may result in words being partially trimmed. The following figure shows the effect of this setting on a TextBlock similar to the one defined above.
When is set to WordEllipsis, text is trimmed and continued with an ellipsis at the end of the first full word closest to the trimming edge. This setting will not show partially trimmed words, but tends not to trim text as closely to the trimming edge as the CharacterEllipsis setting. The following figure shows the effect of this setting on the TextBlock defined above.
When is set to None, no text trimming is performed. In this case, text is simply cropped to the boundary of the parent text container. The following figure shows the effect of this setting on a TextBlock similar to the one defined above.
Windows 8 Consumer Preview, Windows Server 8 Beta, Windows 7, Windows Server 2008 SP2, Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements. | <urn:uuid:142c57b8-2daf-4b0e-af94-d1514b3b4bb4> | 2.71875 | 561 | Documentation | Software Dev. | 43.3908 |
Math Helps Forecast Crimes
April 30, 2012
Mathematicians are helping police find the locations where future crime is most likely to occur.
Saving Time, Money & Jobs
December 13, 2010
Operations researchers improved the efficiency of school bus routes while minimizing the amount of time the students ride. Researchers calculated travel distances to and from various pickup points and consulted census and district maps that show roads, railroads and rivers to find the best routes, eliminating two bus runs and saving thousands of dollars the first year.
Submerged In Oil
October 11, 2010
Physical oceanographers and geophysicists are using a robotic submarine to study the recent Gulf of Mexico oil spill in order to find how much oil is hidden beneath the surface. The submarine, a machine engineered to manipulate density and fitted with sensors to detect depth, location and methane levels traveled one mile below the surface and came within three miles of the spill, sampling the water for analysis.
Phantom Traffic Jams
May 24, 2010
Mathematicians explain how traffic jams form without apparent cause.
Life On Mars
April 12, 2010
Atmospheric scientists and physicists discover lightning on mars using a unique detector
Inside the Wind
November 20, 2009
Aerospace engineers use wind tunnel to study hurricane-strength winds.
Smart Bridge Keeping Drivers Safe
November 06, 2009
Civil engineers installed approximately 400 sensors in a bridge to monitor how corrosion, temperature and traffic loans impact the structure.
July 17, 2009
Researchers found that bacteria can initiate ice formation when super-cooled water droplets condense around the microbes and found evidence of these microbes in snow and rain samples from around the world.
Science of Origami
September 26, 2008
Mathematicians and Artists Use Algorithms to Make Complicated Paper Sculptures
NASA Saving Lives
September 12, 2008
Earth Scientists and Meteorologists Create Historically-Based, Realistic Weather Animations
Knowing Where Tornadoes Will Strike
August 01, 2008
Meteorologists recently studied the effect of gravity waves on tornado formation. They found that when gravity waves push down on rotating thunderstorms the storm compresses and spins faster. Being able to recognize and track gravity waves before they reach thunderclouds allows meteorologists to better predict tornadoes, increasing both the accuracy of their predictions and the amount of warning time that they can provide.
Creating 21st Century Video Games
November 01, 2007
A computer science student created an updated form of the classic video game Pong. The ball appears to move unpredictably, but is actually governed by algorithms that analyze the fluid dynamics of actual plasmas. Careful programming that considers the plasmaýs mathematical properties allows players to activate a vacuum effect or plasma jet that moves the ball in physically realistic ways as well.
Ice, Ice, Baby!
February 01, 2007
When droplets of melted snow drip down an icicle, they release small amounts of heat as they freeze. Heated air travels upwards and helps slow down the growth of the icicle's top, while the tip is growing rapidly. Knowledge of the mathematical equations that govern icicle growth -- the same that apply to stalactites -- could help in the prevention of icicle formation on power lines.
Rip Current Secrets Revealed
August 01, 2006
Rip currents flow in very erratic patterns, not in steady courses as previously believed -- which may help explain why they can be so dangerous even for experienced swimmers. Oceanographers have discovered the behavior by tracking the motion of colored dye added to a wave pool generating rip currents.
The Mystery of Black Holes
December 01, 2005
A satellite called Swift is revealing that black holes have a messier birth than previously thought. Instead of being created in one instant, astrophysicists now believe after a star dies and collapses -- ultimately forming a black hole -- it continues to cause havoc. The baby black hole devours material while at the same time spewing it back out, a process that is revealed in multiple outbursts of gamma rays.
Underwater Weather Watchers
January 01, 2005
Researchers are now collecting valuable information about ocean weather from a fleet of cost-effective instruments called Argo floats. Using hydraulic fluid in internal and external sacs, each float sinks about a mile and a half underwater. Every ten days, the float rises to the surface and transmits information on the ocean temperature and salt content. Researchers hope Argo will improve the ability to forecast the paths of hurricanes and where they will make their landfall. | <urn:uuid:05d312c1-8d75-40d4-8127-f133348f150f> | 2.984375 | 929 | Content Listing | Science & Tech. | 27.919861 |
Like Jupiter, it is a Gas Giant and so its visible surface is not solid. It is most well known for its dramatic and beautiful ring system. The rings are not solid, but are made up of many millions of small lumps of ice and rock, varying from a few centimetres to several metres across. These are all orbiting around Saturn together.
Although they look very impressive, the rings are only about 1 km thick, compared to 250,000 km in diameter!
The first space-probe to go to Saturn was Pioneer 11 in 1979, but there have been several others since.
|Facts and Figures||Mercury||Venus||Earth||Mars||Jupiter||Saturn||Uranus||Neptune|
|Orbital Distance (AU)1||0.38||0.72||1.0||1.52||5.2||9.45||19.2||30.06|
|Mass (Earth Masses)2||0.055||0.82||1.0||0.11||318||95.2||14.5||17.1|
|Surface Gravity (g)3||0.38||0.91||1.0||0.38||2.34||0.93||0.92||1.12|
|Surface Temperature||-200 to|
|460 °C||-80 to|
|-110 °C||-140 °C||-190 °C||-200 °C|
|Number of moons||0||0||1||2||63||60||27||13| | <urn:uuid:57487240-cce2-4531-9d88-611026d96252> | 3.65625 | 342 | Knowledge Article | Science & Tech. | 111.868995 |
Researchers examining DNA evidence gathered from permafrost soil samples collected north of Fairbanks, Alaska say that the woolly mammoth may have survived for thousands of years longer than the fossil record indicates. Writing in the Proceedings of the National Academy of Sciences, the researchers suggest central Alaska was still home to living mammoths as recently as 7,500 to 10,500 years ago. Those new dates mean that people and mammoths could have co-existed in what is now America for over 3500 years. We'll find out more.
Produced by Annette Heist, Senior Producer | <urn:uuid:203dfd2f-1845-4e56-b2bb-18c56bf8d4b3> | 3.484375 | 116 | Truncated | Science & Tech. | 41.135066 |
J. Emmett Duffy, a professor at the Virginia Institute of Marine Science and the College of William and Mary, writes from the coral reefs of Belize, where he is studying sponge-dwelling snapping shrimps.
Sunday, July 8
As the sun breaks the horizon, I sit in a wooden chair at the edge of the backreef, an eye on the weather horizon, gratefully sipping the first strong coffee and gauging what the day has in store. Soothed by the fresh breeze and the muffled thud of the surf on the reef, half-watching a lone frigate bird high overhead and a hermit crab lumbering past my bare foot through a miniature jungle of beach vines and flotsam, it feels like home. It’s my 14th trip to this speck of land at the ocean’s edge, and this has been my morning ritual for years, a rare quiet spot in the tumbling stream of modern life to let the mind unreel and reflect.
We are now fully shifted into Plan B mode. The social shrimps that we came searching for, that have dominated these reefs for at least 20 years, are gone. Scrambling to shift course, we put together a hasty plan to document the change quantitatively. Yesterday morning we began carrying out that plan, collecting 10 bags of coral rubble from the first of six reefs to be sampled and spending the afternoon in the rustic lab, sorting out our quarry. The diving is sublime — idyllic seascapes of coral boulders over brilliant white sand and turtle grass, swaying soft corals and rope sponges, mounds of finger coral in the bright shallows. Fish are plentiful, shoals of grunts and surgeonfish flowing over the reef contours, even a sea turtle foraging over the top of one reef. Back at the lab it’s a laborious process getting under the surface, into the little-known center of biodiversity within the reef structure. But we’re rewarded by a constant stream of small surprises: bizarre undulating flatworms, a rainbow-colored sea slug, a tiny octopus that flashes iridescent color changes like a hallucination. And then there is the abundance of small shrimp.
Today is another marathon. We sample two reefs, taxing work in the choppy weather and strong surge, inhale a hearty lunch prepared by our wonderful cook, Martha, and then switch into lab mode for the long haul of extracting the tiny, elusive shrimp from the sponges and processing them. Our five-member team is now a well-oiled machine, working in assembly-line mode, each with a specific responsibility. This includes identifying shrimp under the microscope, removing subsamples for DNA analyses of genetic relatedness and social structure, measuring and preserving samples of the sponges they came from and carefully documenting all collection data. Even with the efficient division of labor, we’re all seeing double with exhaustion by the time we batten down the lab windows and turn out the light around midnight. This is our routine, from 7:30 a.m. until near midnight for eight days, a point that frequently seems lost when I tell people I’m away for a research trip to the reefs of the Caribbean.
In the morning, I return to my station by the backreef for a few minutes of quiet at daybreak. Strong wind from the southeast, overcast skies and intermittent drizzle. But no lightning so far. We can work. Looking back through my records from more than a decade, I calculate that 75 percent of our shrimp collections in this area consisted of social species — three out of every four specimens we collected. Now there are none, save for a few small colonies of one partly social species. It’s extraordinary. The finding puts into perspective a parallel and also puzzling pattern that we observed in Jamaica. Sampling there in 2008, we found abundant large colonies of social shrimp, but earlier this year colonies were few and much smaller in size. On the Caribbean side of Panama, our colleagues noted a similar disappearance of one of the social species over a few short years.
It now seems clear that a regional decline of social shrimp is under way. And it’s part of a larger pattern of change. Below the deceptively sunny surface of the tropical sea, the loss of social shrimp is only the latest signal of a global ocean ecosystem on the brink of profound change. I and my colleagues everywhere have watched with alarm the astonishingly rapid transformation of the world’s coral reefs, the crown jewels of the planet’s encompassing ocean, over little more than a single human generation. When I began graduate school in 1985, the transformation was only just dawning on us. Most of us got into this business because of what can only be called a love affair with the ocean and its life. But we have been drawn into the unwelcome role of witnessing and documenting the death spiral of reefs and struggling to find some hope for keeping them alive.
As Roger Bradbury wrote bluntly in an Op-Ed article in The New York Times a few days ago, that hope is proving to be a phantom. Coral reefs are dying at our own hands. The murder weapons — fossil fuel consumption and food production — are the basic engines of human economic growth. Relentless harvesting of grazing fishes releases algae and seaweeds that overgrow corals. Rising global temperatures, guaranteed for decades to come by the legacy of greenhouse gases we’ve already released, are already killing corals, which typically live near their upper thermal tolerances. The acidification of the ocean by the same greenhouse gas emissions is expected to dissolve the coral skeletons that create reefs in the first place. Once that complex structure erodes, we are left with flat rock pavements covered by scrubby algae, and biodiversity is accordingly reduced to a fraction of what a healthy reef supports.
Why worry about saving reefs? We frequently hear that they protect coastlines, support tourism and fisheries in the developing world and influence the global carbon budget. These are all true enough and important. But we really care about reefs, we fear for them, because they are exquisitely beautiful and magical undersea gardens of Eden, full of almost unimaginable life-forms that wake something essential in us. They show us, more than perhaps any other ecosystem, what the primeval fire of life is capable of, what it has in fact done over incomprehensible time spans, which we are now undoing permanently. My fear is that a more of us are growing up estranged from the benefits of wild nature and, lacking personal experience of their value, will not even know what we are losing, much less work to preserve and nurture it.
The shrimp we study are admittedly only small players in the drama of the reef, but they are bellwethers of the fundamental changes under way all around us. Our hope is that the new research direction that circumstances have forced on us will help provide some answers to what is driving that change and where we’re headed. | <urn:uuid:85231c52-295c-4dff-8f70-15c900904cf9> | 2.8125 | 1,448 | Nonfiction Writing | Science & Tech. | 46.84544 |
In 2008, the solar cycle plunged into the deepest minimum in nearly a century. Sunspots all but vanished, solar flares subsided, and the sun was eerily quiet. As 2011 unfolds, sunspots have returned and they are crackling with activity. On February 15th and again on March 9th, Earth orbiting satellites detected a pair of "X-class" solar flares--the most powerful kind of x-ray flare. The last such eruption occurred back in December 2006. | <urn:uuid:174c30a1-4228-4db1-a84e-81b36bdd3a4f> | 2.78125 | 100 | Truncated | Science & Tech. | 58.506 |
May 17, 2013
The Navy can build a $100 million submarine training range off the coast of Southern Georgia and Northern Florida, a federal judge ruled Monday.September 11, 2012, Tuesday
A volcanic eruption in India may have been responsible for the disappearance of many marine animals about 200,000 years before the dinosaurs met their end.September 11, 2012, Tuesday
What to do with a lioness found living with cubs in suburban Nairobi, Kenya? Euthanasia may be the best solution.September 11, 2012, Tuesday
Dry conditions across the country, including Long Island, are worrying the botanists closely monitoring the area’s six populations of sandplain gerardia.September 05, 2012, Wednesday
Randall Irmis , curator of paleontology at the Natural History Museum of Utah and an assistant professor at the University of Utah , is investigating the rise of dinosaurs in southeastern Utah.September 04, 2012, Tuesday
Concluding a long effort to take gray wolves in the Northern Rockies off the endangered species list, the federal Fish and Wildlife Service lifted protections for most Wyoming wolves.August 31, 2012, Friday
American citizens seem to do as good a job as government scientists in selecting candidates for federal protection.August 30, 2012, Thursday
American citizens seem to do as good a job as government scientists in selecting candidates for federal protection.August 29, 2012, Wednesday
The federal government is about to strike a wolf management plan with Wyoming. But whether it’s enough to guarantee a sustainable population is far from clear.August 22, 2012, Wednesday
Two episodes of a Sportsman Channel show criticize a delay in allowing wolf hunts, but fail to explain the conflict behind it.August 21, 2012, Tuesday
SEARCH 3793 ARTICLES ABOUT ENDANGERED AND EXTINCT SPECIES:
In Hawaii, at least 4 endangered monk seals have been found violently murdered since the end of 2011.
Last year, the Lahontan cutthroat trout became the first confirmed catch of a fish that for decades was believed to have gone extinct.
A Stanford professor discusses the science and ethics of resurrecting extinct species.
Tens of thousands of African elephants are killed annually, the continent’s worst wildlife crisis in decades.
As many species facing extinction have waited for years to be protected by the United States, the Fish and Wildlife Service has pledged to decide the fates of all the backlogged candidates by 2018.
Subscribe to an RSS feed on this topic. What is RSS? | <urn:uuid:ce07a523-9bd9-4a01-9376-7787ae7b1288> | 2.859375 | 516 | Content Listing | Science & Tech. | 41.834364 |
Professor John H. Lienhard
PI at MIT
Professor Greg Rutledge
PI at MIT
Professor Hassan A. Arafat
PI at Masdar Institute
This project is focused on the development of a membrane distillation (MD) desalination technology. MD is a method of thermal desalination whereby a hot, saline, feed stream is passed over a microporous hydrophobic membrane . The membrane is a thin polymer typically made of Teflon or polypropylene. The temperature difference between the two sides of the membrane leads to a vapor pressure difference that causes water to evaporate and pass through the pores. The water is held back by surface tension as the fluid forms a meniscus on the small pores. This pressure limits the pressure difference across the membranes and is primarily governed by the contact angle of the material and the pore size. MD systems can be run in a variety of configurations, which govern how fluid is collected from the permeate side. There is direct contact MD (DCMD), air gap MD (AGMD), sweeping gas MD (SGMD). SGMD is typically used for removing volatile vapors and is typically not used in desalination.
MD configurations (DCMD, AGMD, and VMD) have been analyzed from an energy efficiency standpoint and VMD was found to have fundamentally limited performance, due to the low condensing temperatures which limit how much heat can be recovered from the permeate vapor. AGMD and DCMD have the potential to produce low-cost water if properly optimized. Multi-stage, multi-pressure, cycles for VMD will be investigated for their energy efficiency to reduce the effect of low saturation temperature.
This research project has several key aspects of relevance to Masdar Institute's mission as well as Abu Dhabi, as it addresses sustainable energy (Solar and Wind) utilization and clean water supply. The project addresses a promising new technology for water desalination (membrane distillation). The research will also help in educating participating students to innovate in desalination system design and it will establish new capacity in the UAE. | <urn:uuid:a5ff5a7c-9d2e-4b2e-8d63-cac49b6118eb> | 2.96875 | 425 | Academic Writing | Science & Tech. | 29.820336 |
The Barents Sea is a sub-Arctic ecosystem located between 70 and 80ºN. It connects with the Norwegian Sea to the west and the Arctic Ocean to the north. The average depth is 230 m and the maximum depth is approximately 500 m at the western entrance. The general pattern of circulation (Figure 2.1.1) is strongly influenced by this topography, and is characterised by inflow of relatively warm Atlantic water, and coastal water from the west. This current divides into two branches: 1) a southern branch that flows parallel to the coast and eastwards towards Novaya Zemlya; and 2) a northern branch that flows into the Hopen Trench. The Coastal Water has more fresh-water runoff and a lower salinity than the Atlantic water; it also has a stronger seasonal temperature signal. In the northern region of the Barents Sea, fresh and cold Arctic waters flow from northeast to southwest. Atlantic and Arctic water masses are separated by the Polar Front, which is characterised by strong gradients in both temperature and salinity. There is large inter-annual variability in ocean climate related to variable strength of the Atlantic water inflow, and exchange of cold Arctic water. Thus, seasonal variations in hydrographic conditions can be quite large. | <urn:uuid:684fcbf0-c414-4cdb-85f7-9108e4e36fa3> | 3.859375 | 261 | Knowledge Article | Science & Tech. | 46.885897 |
A rapidly rotating super massive black hole has been found in the heart of a spiral galaxy by ESA’s XMM-Newton and NASA’s NuSTAR space observatories, opening a new window into how galaxies grow. Super massive black holes are thought to lurk in the center of almost all large galaxies, and scientists believe that the evolution of a galaxy is inextricably linked with the evolution of its black hole. How fast a black hole spins is thought to reflect the history of its formation. In this picture, a black hole that grows steadily, fed by a uniform flow of matter spiraling in, should end up spinning rapidly. Rapid rotation could also be the result of two smaller black holes merging. On the other hand, a black hole buffeted by small clumps of material hitting from all directions will end up rotating relatively slowly. These scenarios mirror the formation of the galaxy itself, since a fraction of all the matter drawn into the galaxy finds its way into the black hole. Because of this, astronomers are keen to measure the spin rates of black holes in the hearts of galaxies. One way of doing so is to observe X-rays emitted just outside the ‘event horizon’, the boundary surrounding a black hole beyond which nothing, including light, can escape.
The main point of scientific interest is the mechanics of making the black hole to spin as the can reveal the secrets of the galaxy’s history:
Space Agency’s XMM-Newton X-ray satellites — have calculated the spin rate of this particular black hole, which is dragging all those stars and other nebula fragments into it, like water swirling into a shower drain. ”This is the first time anyone has accurately measured the spin of a supermassive black hole,” said lead author Guido Risaliti. “The black hole’s spin is a memory, a record, of the past history of the galaxy as a whole.” So how fast are we talking? According to the team’s calculations, the outer edges of NGC 1365 are being whipped around at about 84 percent of the speed of light. Most galaxies spin at a much slower rate than that. In other words, enormous stuff like stars and gas giants are traveling millions of miles against their will — in the blink of an eye. A cosmic spin cycle, if you will. How did NGC 1365′s black hole start spinning so fast to begin with? The principle at work here is called the conservation of angular momentum. It’s why a figure skater can spin in place faster when he pulls his arms closer to his body, and why a little girl can get really high on a playground swing if she tucks her legs in at the right time.
Another important thing is discoveries directly related to supernova explosions:
Black holes are created when a supernova explosion destroys a massive star. Scientists have discovered dozens of black holes, but all of them are already formed. So, when scientists recently saw different distorted remains of a supernova, they knew it something special. What the scientists believe they observed was the infant phases of a black hole, or the youngest black hole ever recorded in the Milky Way galaxy. Caught on film by NASA’s Chandra X-ray Observatory, the “remnant,” or W49B, is seen as a vibrant swirl of blues, greens, yellows, and pinks. As seen from Earth, it is about 1,000-years-old and is located roughly 26,000 light years away. A typical black hole, like SS433, is thought to be between 17,000- and 21,000-years-old, as seen from Earth. ”W49B is the first of its kind to be discovered in the galaxy,” Laura Lopez, who led a study on the remnant at the Massachusetts Institute of Technology, said in a statement. “It appears its parent star ended its life in a way that most others don’t.”
Finally, by discovering the secrets of space we can understand the dynamics of its creation and also find possible solution for solving global problems in Earth. Black hole discoveries is a positive step to this direction.
- Speedy black hole holds galaxy’s history
- The supermassive black hole spinning at nearly the speed of light
- Monster Black Hole's Spin Revealed for 1st Time
- NASA data may have uncovered galaxy's youngest black hole
- First Time Ever Scientists See Black Hole!
- Ultrafast Stars Discovered Racing Through Milky Way
- 5 Insane Sci-Fi Weapons That Now Exist in Reality
- 10 Mind-Bending Facts About Black Holes
- Muse - Supermassive Black Hole - Lyrics
- The Largest Black Holes in the Universe
- Travel INSIDE a Black Hole
- Tracking trains with satellite precision
- SMOS: the global success story continues
- ESA chooses instruments for its Jupiter icy moons explorer
- A cool discovery about the Sun’s next-door twin
- Securing operational EU funding for GMES Copernicus
- Supermassive Black Hole [alternative live version] (Video)
- Black Hole Galaxy Sculptor
- The Black Hole
- Birth of a Black Hole
- How Can Space Expertise Improve Car Performance..?
- Euclid Space Telescope: Why Is The Universe Expanding At An Accelerating Rate..?
- Orion: ESA And NASA To Carry Astronauts Further Into Space..!
- European High School Students And Satellites: The Astronauts Of Tomorrow..!
- CryoSat: It Is Not Only The Polar Sea Ice...
- The Third European Deep-Space Station For Tracking Satellites Will Be Inaugurated On Dec. 18 2012..!
- Antarctica And Greenland SOS: The Combined Rate Of Ice Sheet Melting Is Increasing..!
- International Space Station (ISS): Positioning SOLAR Instrument For A Better View Of The Sun…
- Discovering New Species: When Astronauts Return With A Special Type Of Woodlouse…
- European Space Sector: Investing In Fields With An Immediate Impact On The Economy..!
- Measuring And Mapping The Strength Of Gravity On Earth… | <urn:uuid:e48d24a5-c96b-4329-a093-cbb08ec5cd35> | 3.9375 | 1,289 | Content Listing | Science & Tech. | 52.427518 |
Real Science for Real People
What Playing In The Mud Can Reveal
Editor’s note: Beth Ravit has been contributing science-related articles to Hackensack Tidelines for years. In light of her recent achievement—the attainment of her doctorate degree in environmental science—she was asked to focus this issue’s “Real Science” on her own Meadowlands research.
By Dr. Beth Ravit
(aka The Mud-slinger)
I love to play in the mud. During the past four years I have been an environmental science graduate student at Rutgers University, and on June 30, 2004, I successfully defended my Ph.D. thesis. Since the majority of my thesis research took place in the Hackensack Meadowlands, I thought I would take this opportunity to tell you about my work.
I am very interested in ecosystem functions such as the movement of carbon (C) and nitrogen (N) through the environment [sort of like how water moves through the water cycle]. These cycling processes are critically important due to the global increase in the release of carbon dioxide (CO2) and N. Salt marshes are important components of these cycles.
Plants absorb CO2, which is used in photosynthesis to produce more biomass (living tissue). In salt marshes, over 50% of the plant biomass is below ground in the root system. When the plant dies, microbes living in the sediment decompose the root tissues. These decomposition processes release (CO2) and methane (CH4), both of which are potent greenhouse gases. However, also living in the sediments are different microbes that are able to take up these greenhouse gases, and so under natural conditions the C cycle remains in balance. Salt marshes are also important in N cycling because under the anaerobic (no oxygen) conditions that are found in flooded sediments, microbes transform nitrate (a form of nitrogen) to inert N2 gas. The N2 gas is then released back into the atmosphere.
My research addressed two questions: 1) Are there different sediment microbial communities associated with Phragmites versus Spartina grasses? and 2) Are there differences in sediment microbial communities in a disturbed marsh ecosystem versus an undisturbed marsh ecosystem?
I analyzed sediment microbial community structure (which microbes live there) and function (what can they do), and had some very interesting results. Using sediment taken from both disturbed and undisturbed systems, I added a brominated flame retardant contaminant (see Tidelines, Winter 2004) and then incubated the samples anaerobically in the laboratory. Spartina sediments from both sites biotransformed the contaminant more quickly than either Phragmites sediments or unvegetated mud. We're not exactly sure why this happens, but I am setting up new experiments to try and find out what is different about the Spartina root zone.
I also found differences in how the sediments responded to the addition of C and N compounds. Sediments from the undisturbed salt marsh systems (Mullica and Maurice River estuaries) had more microbial activity related to C and N cycling than did the sediments from the Meadowlands. We think this is because the Mullica and Maurice Rivers drain the Pinelands, which is a low nutrient system. Under low nutrient conditions the microbial community would respond quickly to nutrient inputs. The lower response in Meadowlands sediments suggests that nutrient loads are higher in the Hackensack than in the Mullica or Maurice Rivers.
I hope that the work I'm doing can ultimately be incorporated into salt marsh restoration projects, so when we restore damaged estuarine systems we set goals for the sediment restoration as well as for above ground habitats. It is in the mud that critical microbial processes are occurring, and these processes have the potential to affect the cycling of C and N, which at this point in time has global consequences.
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One aspect of tundra plants that is highly sensitive to slight changes in temperature is phenology, the timing of key life-history events such as bud burst, leaf growth, flowering etc. In highly seasonal environments, such as the Arctic, timing key phenological events with the appropriate climate is essential for plant success. Plants whose phenology is regulated by unchanging internal factors or daylength will be unable to respond to changes in season length and will be replaced by species responding to other cues. The ITEX phenology, growth and community data analyzed to date show responses that in many ways mirror patterns seen along latitudinal temperature gradients. However, changes are too subtle and too variable to be detected by most individual-site studies, some after more than a decade of warming.
ITEX as an observing network provides a unique opportunity to evaluate plant phenology changes at a global scale across the tundra biome. In this working group we will evaluate changes in plant phenology across the tundra biome over the past 10-15 years in two ways: 1) comparing ambient-temperature plots versus plots subject to long-term experimental warming, and 2) comparing measurements of ambient-temperature plots taken during the mid 1990's International Polar Year. The aim of these analyses is to help us answer one of the driving questions of arctic biology in the face of climate warming, "What form will new arctic plant communities take and what are the processes driving these changes?"
More information about this research project and participants. | <urn:uuid:133d70e9-45d5-4a65-b898-f935bc328aab> | 2.75 | 310 | Academic Writing | Science & Tech. | 23.311492 |
PostgreSQL manages database access permissions using the concept of roles. A role can be thought of as either a database user, or a group of database users, depending on how the role is set up. Roles can own database objects (for example, tables) and can assign privileges on those objects to other roles to control who has access to which objects. Furthermore, it is possible to grant membership in a role to another role, thus allowing the member role to use privileges assigned to another role.
The concept of roles subsumes the concepts of "users" and "groups". In PostgreSQL versions before 8.1, users and groups were distinct kinds of entities, but now there are only roles. Any role can act as a user, a group, or both.
This chapter describes how to create and manage roles. More information about the effects of role privileges on various database objects can be found in Section 5.6. | <urn:uuid:8e748fea-9831-459c-b1cf-19a9f139a648> | 3.21875 | 187 | Documentation | Software Dev. | 48.728916 |
Science & Astronomy Archive
04 April 2013, 07:00 AM ET
Mars is on the other side of the sun from Earth, making communications difficult.
03 April 2013, 06:36 PM ET
Astronomers know more about what dark matter is not than what it actually is.
03 April 2013, 05:36 PM ET
The potential dark matter find announced today wouldn't have been possible without the International Space Station.
03 April 2013, 04:57 PM ET
NASA Administrator Charles Bolden has high praise for the first results from the space station's Alpha Magnetic Spectrometer.
03 April 2013, 02:42 PM ET
SPACE.com's Miriam Kramer asked Nobel prize winner and NASA's AMS-02 principle investigator Samuel C.C. Ting about the performance of the Alpha Magnetic Spectrometer aboard the ISS (a mission that was almost scrapped after the Columbia Disaster).
03 April 2013, 02:06 PM ET
A panel of scientists discuss the issues facing the search for and understanding of planets orbiting far-distant stars in part one of an eight-part series.
03 April 2013, 01:36 PM ET
A space station particle detector has found hints of dark matter, but experiments deep below the Earth's surface may directly detect it.
03 April 2013, 12:03 PM ET
Advanced cameras helped scientists spot the phenomenon.
03 April 2013, 11:23 AM ET
This stunning space wallpaper reveals W3, which is an enormous stellar nursery about 6200 light-years away in the Perseus Arm, one of the Milky Way galaxy’s main spiral arms, that hosts both low- and high-mass star formation.
03 April 2013, 11:00 AM ET
A space station particle detector has found hints of elusive dark matter in cosmic radiation.
03 April 2013, 09:54 AM ET
The space agency will unveil the first results from the $2 billion antimatter-hunting Alpha Magnetic Spectrometer on the International Space Station.
03 April 2013, 07:37 AM ET
Night sky photographer Martin Pugh in Australia captured this amazing view of the Pencil Nebula in March 2013.
03 April 2013, 07:33 AM ET
The Cosmic Microwave Background radiation tells us the age and composition of the universe and raises new questions that must be answered.
03 April 2013, 07:26 AM ET
New supercomputer simulations show how spiral galaxies like the Milky Way get, and keep, their skinny, star-studded arms.
03 April 2013, 07:01 AM ET
Here are some of the most puzzling mysteries facing astronomers today.
02 April 2013, 08:30 PM ET
Backpack-friendly plane flies over Costa Rican volcano for NASA.
02 April 2013, 06:43 PM ET
The science results come from the $2 billion Alpha Magnetic Spectrometer on the International Space Station.
02 April 2013, 04:48 PM ET
See the space station's Alpha Magnetic Spectrometer, a $2 billion machine to catch cosmic rays in orbit.
02 April 2013, 03:52 PM ET
A collision may have spun Saturn's fourth moon around 180 degrees.
02 April 2013, 02:38 PM ET
Though dark matter is invisible, photos of galaxy clusters and gravitational lensing hint at its nature.
02 April 2013, 01:21 PM ET
Scientists Elena D'Onghia, Mark Vogelsberger and Thiago ize have used the Harvard FAS Supercomputer Odyssey to put a 100 million animated stars in motion.
02 April 2013, 01:17 PM ET
This ghostly space wallpaper shows an object known as HH 151, a bright jet of glowing material trailed by an intricate, orange-hued plume of gas and dust.
02 April 2013, 01:08 PM ET
Take an in-depth look at the Alpha Magnetic Spectrometer will hunt dark matter, cosmic rays and antimatter galaxies.
02 April 2013, 10:40 AM ET
Human cells in space look more like art than science.
02 April 2013, 09:26 AM ET
Astronomers have detected a black hole consuming the outer layers of a brown dwarf or a giant planet. Observations of galaxy NGC 4845 by ESA's Integral Space Observatory and XMM-Newton revealed an x-ray flare consistent with black hole activity. | <urn:uuid:512200be-1385-453f-9e48-6ac2209dd864> | 2.734375 | 902 | Content Listing | Science & Tech. | 64.514773 |
Tracing Math's Evolution
Print this page, and use it to help you complete the lesson.
Your group will choose one of the mathematicians you researched and develop a presentation about him/her. You will share your presentation with the rest of the class.
Decide on jobs for each member of your group. All of you should be involved in both preparation and presentation.
In your presentation, try to answer following questions:
- Where was this mathematician born?
- What was his/her date of birth?
- Where was he/she educated?
- What was his/her contribution to mathematics?
- Why is this an important contribution?
- Do you know why he/she chose his/her career?
- Do you know if he/she made his/her living from mathematics?
- Was he/she famous during his/her lifetime?
- Where and when did he/she die?
- What impresses you most about this mathematician?
Did your mathematician invent anything that is used today?
Was his/her work used in other inventions?
If you can find any objects or pictures of objects that are related to your mathematician's work or life, use them as part of your presentation. | <urn:uuid:c0d3c49c-0f41-49ee-a237-35db9d32a7cd> | 4 | 255 | Tutorial | Science & Tech. | 60.761111 |
Narrator: This is Science Today. Commercial harvesting of fish and wildlife is quickly reshaping the wild populations that remain due to the practice of harvesting vast numbers of species and targeting large, reproductively mature individuals. Those were the findings of a novel study led by Chris Darimont of the University of California, Santa Cruz, which coincidentally was released during the 200th year of Charles Darwin's birth.
Darimont: This work comes at a timely period in which scientists are recognizing that Darwin was indeed right - and in fact, organisms can change within populations very, very quickly and as it turns out, our work shows that among the most rapidly changing organisms on the planet, ones that are changing so fast that even Darwin might be shocked, really underscores the presence and power of natural selection acting in an increasingly unnatural world. A world in which humans are becoming a dominant selective force.
Narrator: For Science Today, I'm Larissa Branin. | <urn:uuid:142772dd-2f58-474f-9103-a3b0275640cd> | 2.90625 | 194 | Audio Transcript | Science & Tech. | 27.488333 |
|If a straight line is cut at random, then the square on the whole equals the sum of the squares on the segments plus twice the rectangle contained by the segments.|
|Let the straight line AB be cut at random at C.
I say that the square on AB equals the sum of the squares on AC and CB plus twice the rectangle AC by CB.
|Describe the square ADEB on AB. Join BD. Draw CF through C parallel to either AD or EB, and draw HK through G parallel to either AB or DE.||I.46
|Then, since CF is parallel to AD, and BD falls on them, the exterior angle CGB equals the interior and opposite angle ADB.||I.29|
|But the angle ADB equals the angle ABD, since the side BA also equals AD. Therefore the angle CGB also equals the angle GBC, so that the side BC also equals the side CG.||I.5
|But CB equals GK, and CG to KB. Therefore GK also equals KB. Therefore CGKB is equilateral.||I.34|
|I say next that it is also right-angled.|
|Since CG is parallel to BK, the sum of the angles KBC and GCB equals two right angles.||I.29|
|But the angle KBC is right. Therefore the angle BCG is also right, so that the opposite angles CGK and GKB are also right.||I.34|
|Therefore CGKB is right-angled, and it was also proved equilateral, therefore it is a square, and it is described on CB.|
|For the same reason HF is also a square, and it is described on HG, that is AC. Therefore the squares HF and KC are the squares on AC and CB.||I.34|
|Now, since AG equals GE, and AG is the rectangle AC by CB, for GC equals CB, therefore GE also equals the rectangle AC by CB. Therefore the sum of AG and GE equals twice the rectangle AC by CB.||I.43|
|But the squares HF and CK are also the squares on AC and CB, therefore the sum of the four figures HF, CK, AG, and GE equals the sum of the squares on AC and CB plus twice the rectangle AC by CB.|
|But HF, CK, AG, and GE are the whole ADEB, which is the square on AB.|
|Therefore the square on AB equals the the sum of the squares on AC and CB plus twice the rectangle AC by CB.|
|Therefore if a straight line is cut at random, the square on the whole equals the squares on the segments plus twice the rectangle contained by the segments.|
Next proposition: II.5
Dept. Math. & Comp. Sci. | <urn:uuid:21774e62-92fa-40b0-976f-40f0388203b6> | 3.53125 | 595 | Academic Writing | Science & Tech. | 86.448415 |
Chemistry of Carbon
Organic chemistry involves structures and reactions of mainly carbon and hydrogen. Inorganic chemistry deal with interactions of all other pure elements besides carbon, amongst geo/biochemistry. So where does inorganic chemistry of carbon fit in? The inorganic chemistry of carbon also known as inorganic carbon chemistry, is the chemistry of carbon that does not fall within the organic chemistry zone.
Inorganic Chemistry of Carbon
Inorganic carbon is carbon extracted from ores and minerals, as opposed to organic carbon found in nature through plants and living things. Some examples of inorganic carbon are carbon oxides such as carbon monoxide and carbon dioxide; polyatomic ions, cyanide, cyanate, thiocyanate, carbonate and carbide in carbon. Carbon is an element that is unique to itself. Carbon forms strong single, double and triple bonds, therefore it would take more energy to break these bonds than if carbon were to bond to another element.
For carbon monoxide the reaction is as follows:
2C(s) + O2 → 2CO(g) Enthalpy of -110.52 kJ/mol CO
CO and CO2 are both gases. CO has no odor or taste and can be fatal to living organisms if exposed at even very small amounts (about a thousandth of a gram). This is because CO will bind to the hemoglobin that carries oxygen in the blood. CO2 will not become fatal unless living organisms are exposed to larger amounts of it, about 15%. CO2 influences the atmosphere and effects the temperature through the greenhouse gas effect. As heat is trapped in the atmosphere by CO2 gases, the Earth's temperature increases. The main source for CO2 in our atmosphere, amongst many is volcanoes.
Allotropes of Inorganic
The inorganic chemistry of carbon allotropes include diamond, graphite and fullerenes.
Why are some carbon compounds classified as inorganic?
(See text above) Those carbon compounds that are not found naturally.
What is the compound for carbonate, and why is it considered an inorganic compound?
A carbonate compound contains the CO32- ion. These are inorganic compounds because it combines with metal cations, creating ionic compounds.
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||This article needs attention from an expert in Computer science. (November 2008)|
|Part of a series on|
Packing problems are a class of optimization problems in mathematics that involve attempting to pack objects together into containers. The goal is to either pack a single container as densely as possible or pack all objects using as few containers as possible. Many of these problems can be related to real life packaging, storage and transportation issues. Each packing problem has a dual covering problem, which asks how many of the same objects are required to completely cover every region of the container, where objects are allowed to overlap.
In a packing problem, you are given:
- 'containers' (usually a single two- or three-dimensional convex region, or an infinite space)
- A set of 'objects' some or all of which must be packed into one or more containers. The set may contain different objects with their sizes specified, or a single object of a fixed dimension that can be used repeatedly.
Usually the packing must be without overlaps between goods and other goods or the container walls. In some variants, the aim is to find the configuration that packs a single container with the maximal density. More commonly, the aim is to pack all the objects into as few containers as possible. In some variants the overlapping (of objects with each other and/or with the boundary of the container) is allowed but should be minimized.
|Covering problems||Packing problems|
|Minimum set cover||Maximum set packing|
|Minimum vertex cover||Maximum matching|
|Minimum edge cover||Maximum independent set|
Packing infinite space
Many of these problems, when the container size is increased in all directions, become equivalent to the problem of packing objects as densely as possible in infinite Euclidean space. This problem is relevant to a number of scientific disciplines, and has received significant attention. The Kepler conjecture postulated an optimal solution for packing spheres hundreds of years before it was proven correct by Thomas Callister Hales. Many other shapes have received attention, including ellipsoids, Platonic and Archimedean solids including tetrahedra, and unequal-sphere dimers.
Hexagonal packing of circles
These problems are mathematically distinct from the ideas in the circle packing theorem. The related circle packing problem deals with packing circles, possibly of different sizes, on a surface, for instance the plane or a sphere.
The counterparts of a circle in other dimensions can never be packed with complete efficiency in dimensions larger than one (in a one dimensional universe, the circle analogue is just two points). That is, there will always be unused space if you are only packing circles. The most efficient way of packing circles, hexagonal packing, produces approximately 91% efficiency.
Sphere packings in higher dimensions
In three dimensions, the face-centered cubic lattice offers the best lattice packing of spheres, and is believed to be the optimal of all packings. The 8-dimensional E8 lattice and 24-dimensional Leech lattice are also believed to be optimal.
Packings of Platonic solids in three dimensions
Cubes can easily be arranged to fill three-dimensional space completely, the most natural packing being the cubic honeycomb. No other Platonic solid can tile space on its own, but some preliminary results are known. Tetrahedra can achieve a packing of at least 85%. One of the best packings of regular dodecahedra is based on the aforementioned face-centered cubic (FCC) lattice.
Tetrahedra and octahedra together can fill all of space in an arrangement known as the tetrahedral-octahedral honeycomb.
|Solid||Maximum known packing density||Lowest upper bound for lattice packing density|
|octahedra||0.947003...[better source needed]||18/19 = 0.947368...|
Packing in 3-dimensional containers
Spheres into a Euclidean ball
The problem of finding the smallest ball such that disjoint open unit balls may be packed inside it has a simple and complete answer in -dimensional Euclidean space if , and in an infinite dimensional Hilbert space with no restrictions. It is worth describing in detail here, to give a flavor of the general problem. In this case, a configuration of pairwise tangent unit balls is available. Place the centers at the vertices of a regular dimensional simplex with edge 2; this is easily realized starting from an orthonormal basis. A small computation shows that the distance of each vertex from the barycenter is . Moreover, any other point of the space necessarily has a larger distance from at least one of the vertices. In terms of inclusions of balls, the open unit balls centered at are included in a ball of radius , which is minimal for this configuration.
To show that this configuration is optimal, let be the centers of disjoint open unit balls contained in a ball of radius centered at a point . Consider the map from the finite set into taking in the corresponding for each . Since for all , this map is 1-Lipschitz and by the Kirszbraun theorem it extends to a 1-Lipschitz map that is globally defined; in particular, there exists a point such that for all one has , so that also . This shows that there are disjoint unit open balls in a ball of radius if and only if . Notice that in an infinite dimensional Hilbert space this implies that there are infinitely many disjoint open unit balls inside a ball of radius if and only if . For instance, the unit balls centered at , where is an orthonormal basis, are disjoint and included in a ball of radius centered at the origin. Moreover, for , the maximum number of disjoint open unit balls inside a ball of radius r is .
Spheres in a cuboid
Packing in 2-dimensional containers
Packing circles
Circles in circle
Pack n unit circles into the smallest possible circle. This is closely related to spreading points in a unit circle with the objective of finding the greatest minimal separation, dn, between points.
Optimal solutions have been proven for n≤13, and n=19.
Circles in square
Pack n unit circles into the smallest possible square. This is closely related to spreading points in a unit square with the objective of finding the greatest minimal separation, dn, between points. To convert between these two formulations of the problem, the square side for unit circles will be L=2+2/dn.
Optimal solutions have been proven for n≤30.
Circles in isosceles right triangle
Circles in equilateral triangle
Packing squares
Squares in square
Pack n unit squares into the smallest possible square.
Optimal solutions have been proven for n=1-10, 14-16, 23-25, 34-36, 62-64, 79-81, 98-100, and any square integer.
Squares in circle
Pack n squares in the smallest possible circle.
|Number of squares||Circle radius|
Packing rectangles
Identical rectangles in a rectangle
The problem of packing multiple instances of a single rectangle of size (l,w), allowing for 90° rotation, in a bigger rectangle of size (L,W) has some applications such as loading of boxes on pallets and, specifically, woodpulp stowage.
For example, it is possible to pack 147 rectangles of size (137,95) in a rectangle of size (1600,1230).
Different rectangles in a rectangle
The problem of packing multiple rectangles of varying widths and heights in an enclosing rectangle of minimum area (but with no boundaries on the enclosing rectangle's width or height) has an important application in combining images into a single larger image. A web page that loads a single larger image often renders faster in the browser than the same page loading multiple small images, due to the overhead involved in requesting each image from the web server.
An example of a fast algorithm that packs rectangles of varying widths and heights into an enclosing rectangle of minimum area is here.
Related fields
In tiling or tessellation problems, there are to be no gaps, nor overlaps. Many of the puzzles of this type involve packing rectangles or polyominoes into a larger rectangle or other square-like shape.
There are significant theorems on tiling rectangles (and cuboids) in rectangles (cuboids) with no gaps or overlaps:
- An a × b rectangle can be packed with 1 × n strips iff n divides a or n divides b.
- de Bruijn's theorem: A box can be packed with a harmonic brick a × a b × a b c if the box has dimensions a p × a b q × a b c r for some natural numbers p, q, r (i.e., the box is a multiple of the brick.)
The study of polyomino tilings largely concerns two classes of problems: to tile a rectangle with congruent tiles, and to pack one of each n-omino into a rectangle.
A classic puzzle of the second kind is to arrange all twelve pentominoes into rectangles sized 3×20, 4×15, 5×12 or 6×10.
Packing of irregular objects
Packing of irregular objects is a problem not lending itself well to closed form solutions; however, the applicability to practical environmental science is quite important. For example, irregularly shaped soil particles pack differently as the sizes and shapes vary, leading to important outcomes for plant species to adapt root formations and to allow water movement in the soil.
See also
- Set packing
- Bin packing problem
- Slothouber-Graatsma puzzle
- Conway puzzle
- Covering problem
- Knapsack problem
- Tetrahedron packing
- Cutting stock problem
- Kissing number problem
- Lodi, A., Martello, S., Monaci, M. (2002). "Two-dimensional packing problems: A survey". European Journal of Operational Research (Elsevier).
- Donev, A.; Stillinger, F.; Chaikin, P.; Torquato, S. (2004). "Unusually Dense Crystal Packings of Ellipsoids". Physical Review Letters 92 (25). doi:10.1103/PhysRevLett.92.255506.
- Torquato, S.; Jiao, Y. (Aug 2009). "Dense packings of the Platonic and Archimedean solids". Nature 460 (7257): 876–879. Bibcode:2009Natur.460..876T. doi:10.1038/nature08239. ISSN 0028-0836. PMID 19675649. More than one of
- Haji-Akbari, A.; Engel, M.; Keys, A. S.; Zheng, X.; Petschek, R. G.; Palffy-Muhoray, P.; Glotzer, S. C. (2009). "Disordered, quasicrystalline and crystalline phases of densely packed tetrahedra". Nature 462 (7274): 773–777. Bibcode:2009Natur.462..773H. doi:10.1038/nature08641. PMID 20010683.
- Chen, E. R.; Engel, M.; Glotzer, S. C. (2010). "Dense Crystalline Dimer Packings of Regular Tetrahedra". Discrete & Computational Geometry 44 (2): 253. doi:10.1007/s00454-010-9273-0.
- Hudson, T. S.; Harrowell, P. (2011). "Structural searches using isopointal sets as generators: Densest packings for binary hard sphere mixtures". Journal of Physics: Condensed Matter 23 (19): 194103. doi:10.1088/0953-8984/23/19/194103.
- Betke, U. & Henk, M. Densest lattice packings of 3-polytopes. Comput. Geom. 16, 157–186 (2000)
- Minkowski, H. Dichteste gitterfo¨rmige Lagerung kongruenter Ko¨rper. Nachr. Akad. Wiss. Go¨ttingen Math. Phys. KI. II 311–355 (1904).
- Croft, Hallard T.; Falconer, Kenneth J.; Guy, Richard K. (1991). Unsolved Problems in Geometry. New York: Springer-Verlag. pp. 108–110. ISBN 0-387-97506-3.
- Eckard Specht (20 May 2010). "The best known packings of equal circles in a square". Retrieved 25 May 2010.
- Specht, Eckard (11 March 2011). "The best known packings of equal circles in an isosceles right triangle". Retrieved 1 May 2011.
- Melissen, J. (1995). "Packing 16, 17 or 18 circles in an equilateral triangle". Discrete Mathematics 145: 333–342. doi:10.1016/0012-365X(95)90139-C.
- Erich Friedman, "Packing unit squares in squares: a survey and new results", The Electronic Journal of Combinatorics DS7 (2005).
- P. Erdős and R. L. Graham, "On packing squares with equal squares", Journal of Combinatorial Theory, Series A 19 (1975), pp. 119–123.
- E G Birgin, R D Lobato, R Morabito, "An effective recursive partitioning approach for the packing of identical rectangles in a rectangle", Journal of the Operational Research Society, 2010, 61, pp. 306-320.
- Honsberger, Ross (1976). Mathematical Gems II. The Mathematical Association of America. p. 67. ISBN 0-88385-302-7.
- Klarner, D.A.; Hautus, M.L.J (1971). "Uniformly coloured stained glass windows". Proceedings of the London Mathematical Society. 3 (23): 613–628.
- C.Michael Hogan. 2010. Abiotic factor. Encyclopedia of Earth. eds Emily Monosson and C. Cleveland. National Council for Science and the Environment. Washington DC
- Weisstein, Eric W., "Klarner's Theorem", MathWorld.
- Weisstein, Eric W., "de Bruijn's Theorem", MathWorld.
Many puzzle books as well as mathematical journals contain articles on packing problems.
- Links to various MathWorld articles on packing
- MathWorld notes on packing squares.
- Erich's Packing Center
- www.packomania.com A site with tables, graphs, calculators, references, etc.
- "Box Packing" by Ed Pegg, Jr., the Wolfram Demonstrations Project, 2007.
- Best known packings of equal circles in a circle, up to 1100
- Solve packaging problem in PHP
- Circle packing challenge problem in Python | <urn:uuid:c2b0b124-3a8d-4640-8733-e7f247070904> | 3.953125 | 3,250 | Knowledge Article | Science & Tech. | 58.511311 |
Family: Papilionidae, Swallowtails view all from this family
Description The larva is green with two false eye spots on the thorax. It has a few blue spots on the first abdominal segment to the eighth segment. It also lives in a leaf shelter. (The larva is almost identical to the caterpillar of the Spicebush Swallowtail (Papilio troilus) except the Spicebush Swallowtail larva has larger false eyes, larger blue spots, and has different host plant preferences. The green chrysalis has a whitish lateral stripe edged with brown above and has two horns on the head. The chrysalis hibernates. The Palamedes Swallowtail has 2-3 broods per year.
Dimensions Caterpillar, to 2" (51 mm).
Habitat Forests & woodlands, Freshwater swamps, marshes & bogs, Meadows & fields.
Range Mid-Atlantic, Southwest, Rocky Mountains, Great Lakes, Texas, Florida, Plains. | <urn:uuid:2026add9-af50-449b-89bc-def3a1b4d73a> | 2.90625 | 211 | Knowledge Article | Science & Tech. | 51.796091 |
Interprets the bitwise representation of
source in memory as if it is the representation of a variable or array of the same type and type parameters as
This is approximately equivalent to the C concept of casting one type to another.
Fortran 90 and later
result = transfer(source, mold[, size])
source- Shall be a scalar or an array of any type.
mold- Shall be a scalar or an array of any type.
size- (Optional) shall be a scalar of type
The result has the same type as
mold, with the bit level representation of
size is present, the result is a one-dimensional array of length
size is absent but
mold is an array (of any size or shape), the result is a one- dimensional array of the minimum length needed to contain the entirety of the bitwise representation of
size is absent and
mold is a scalar, the result is a scalar.
If the bitwise representation of the result is longer than that of
source, then the leading bits of the result correspond to those of
source and any trailing bits are filled arbitrarily.
When the resulting bit representation does not correspond to a valid representation of a variable of the same type as
mold, the results are undefined, and subsequent operations on the result cannot be guaranteed to produce sensible behavior. For example, it is possible to create
logical variables for which
.not. var both appear to be true.
program test_transfer integer :: x = 2143289344 print *, transfer(x, 1.0) ! prints "nan" on i686 end program
Joe Krahn: Fortran uses molding rather than casting.
Casting, as in C, is an in-place reinterpretation. A cast is a device that is built around an object to change it’s shape.
Fortran TRANSFER reinterprets data out-of-place. It can be considered molding rather than casting. A mold is a device that confers a shape onto an object placed into it.
The advantage of molding is that data is always valid in the context of the variable that holds it. For many cases, a decent compiler should optimize TRANSFER into a simple assignment.
There are disadvantages of this approach. It is problematic to define a union of data types because you must know the largest data object, which can vary by compiler or compile options. In many cases, an EQUIVALENCE would be far more effective, but Fortran Standards committees seem oblivious to the benefits of EQUIVALENCEs when used sparingly. | <urn:uuid:3dd913f6-f829-4836-9f9b-e04e6e5cbd41> | 3.34375 | 549 | Documentation | Software Dev. | 44.730481 |
Before we can start star-gazing, we need to define some basic directions and terminology, as well as a system for measuring time. This section also introduces the charts astronomers use to represent the entire night sky.
Background Reading: Stars & Planets, p. 13 & 14 (Star positions); p. 16 & 17 (Appearance of the sky).
Astronomy would be pretty easy, and pretty dull, if the Earth didn't move. In fact, the Earth has several different motions which must be understood in order to do astronomy. One of these motions is the Earth's rotation on its axis; another is the Earth's revolution, or orbital motion, about the Sun.
If you watch the night sky for a few hours, you will see that the stars appear to rotate about a fixed point in the sky (which happens to be near the pole star, Polaris). This motion is due to the Earth's rotation. As the spin of the Earth carries us eastward at almost one thousand miles per hour, we see stars rising in the East, passing overhead, and setting in the West. The Sun, Moon, and planets appear to move across the sky much like the stars.
Because of the Earth's rotation, everything in the sky seems to move together, turning once around us every 24 hours. Ancient astronomers explained this phenomenon by supposing that the Sun, Moon, planets, and stars were attached to a huge celestial sphere, centered on the Earth, which rotated on a fixed axis once per day. Of course, this sphere does not really exist; the Sun, Moon, planets, and stars all fall freely through space, and only appear to move together because of the Earth's rotation. Nonetheless, we still use the concept of the celestial sphere in talking about the positions of stars.
The celestial sphere appears to rotate around a fixed point, the North celestial pole, which is 21.3° above the horizon as seen from Oahu. The point on the horizon directly below the celestial pole is due North, while the opposite direction is South. If you face North, East is on your left and West is on your right. Finally, the Zenith is the point exactly overhead.
Since the apparent rotation of the celestial sphere is due to the actual rotation of the Earth, the North celestial pole is exactly overhead as seen from Earth's North Pole. Likewise, every point on the celestial equator is exactly overhead from some point on the Earth's equator.
Over the course of a year, the Earth makes one complete orbit about the Sun. As a result, the Sun seems to move with respect to the stars, appearing in front of one constellation after another, as shown in the diagram on p. 12 of Stars & Planets. After one year, the Sun is back where it started. The Sun's annual path across the sky is called the ecliptic. Traditionally, the ecliptic was divided into twelve equal parts, each associated with a different constellation of the zodiac.
The night-time sky is just the part of the sky that we see when the islands of Hawaii have turned away from the Sun. As we orbit the Sun, different constellations are visible at different times of the year. In January, for example, the evening sky is dominated by Winter constellations like Orion and Taurus; by the end of the semester, these constellations will appear low in the western sky, and Spring constellations like Leo and Centaurus will be visible instead.
The Earth's axis of rotation is not precisely parallel to its axis of revolution; the angle between them is 23.5°. Consequently, the ecliptic is inclined by the same angle of 23.5° with respect to the celestial equator. This misalignment causes seasons; when the Sun appears North of the celestial equator the Earth's northern hemisphere receives more sunlight, while when the Sun appears South of the celestial equator the northern hemisphere receives less sunlight.
If we could view the Solar System from a point far above the North Pole, we'd see the Earth rotating counter-clockwise on its axis and revolving counter-clockwise about the Sun. Most of the other planets would also appear to rotate counter-clockwise. In addition, the Moon would appear to orbit the Earth in a counter-clockwise direction, as would most other planetary satellites.
In this class, we will use a 24-hour clock instead of writing `am' or `pm'. Since our class meets in the evening, most of the times we will record are after noon, and the 24-hour time is the time on your watch plus 12 hours. For example, our class starts at 19:00 (= 7:00 pm + 12:00), and ends at 22:00 (= 10:00 pm + 12:00). Sometimes we need to record the date and the time together; for example, our first class begins at 01/14/03, 19:00.
Astronomers all over the world use a single time system to coordinate their observations. This system is called Universal Time, abbreviated as UT or UTC. (Greenwich Mean Time, abbreviated GMT, is the same thing as UT.) Universal Time is exactly 10 hours ahead of Hawaii time. To convert 24-hour Hawaii time to UT, you add 10 hours; if the result is more than 24, subtract 24 and go to the next day. For example, our first observing session (weather permitting) will be at 01/21/03, 19:00, or 01/22/03, 05:00 UT. To convert from UT to Hawaii time, you subtract 10 hours; if the result is less than 0, you add 24 and go to the previous day. For example, Mercury will pass in front of the Sun from 05/07/03, 05:13 UT to 05/07/03, 10:32 UT; that's 05/06/03, 19:13 to 05/07/03, 00:32 in our time zone. (Unfortunately, the Sun will have set here on Oahu before this interesting event begins!)
As a rule, we will use 24-hour Hawaii time in this class, and write the time without any time zone. The `UT' symbol will be used only when we want to specify universal time.
Astronomers represent the appearance of the entire sky as seen at some particular place and time by drawing circular all-sky charts. Unfortunately, it's not really possible to capture the appearance of the sky on a flat piece of paper, so reading an all-sky chart and relating it to what you see in the sky is a bit tricky. For example, these charts distort the patterns of stars near the horizon, so you may find it hard to recognize constellations from an all-sky chart. The only way to correct this distortion is to break the sky up into several separate charts (this is the approach used in The Sky Tonight, which we will use to find the constellations). For some purposes, however, it's very convenient to show the entire sky in one chart, so you should learn to read an all-sky chart.
To read an all-sky chart, hold it in front of you with the side labeled `N' at the top. Now imagine you are lying flat on your back with your head pointing North; then East will be on your left, South at your feet, West on your right, and the Zenith right in front of you. Mentally stretch the disk of the chart so that it forms a dome over your position. The positions of stars on this imaginary dome now correspond to their positions in the sky.
|The sky over Honolulu on 01/21/03, 21:00, produced using Your Sky. Stars are shown as dots, with larger dots for brighter stars; the connecting lines show constellations. The symbols show the positions of Jupiter and Saturn. The blue curve is the celestial equator, and the red curve is the ecliptic. The red `x' is used in a review question below. Compass points are shown around the edge of the chart.|
If you try this exercise with the chart shown here, you can get a pretty good idea of how the sky will look on 01/21/03, 21:00. For example, Saturn is near the center of chart, so it will be almost exactly overhead. Jupiter is on the left side of the chart, about one-third of the distance from the edge to the center, so it will be visible in the East, about one-third of the way from the horizon to the Zeneth. The North Star, Polaris, is near the top of the chart, so it will be visible in the North; the Little Dipper hangs down toward the horizon from Polaris, and it will only be visible if we have a good view toward the North (which Kapiolani park, alas, does not).
Note: this is an advanced topic. We won't have much use for celestial coordinates in this class, but you'll see them mentioned from time to time.
Just as latitude and longitude can be used to specify any point on the Earth's surface, two celestial coordinates can be used to specify any point on the celestial sphere. Imagine starting from the point on the sky the point where the Sun, moving North, crosses the celestial equator (this is the point labeled `0 h' in the chart above). To reach any given point on the celestial sphere, you could first travel along the celestial equator, and then towards one of the celestial poles, until you reach your destination. The angle you've traveled along the equator is called the right ascension; it's measured in units of hours, where 1 hour = 15°. The angle you've traveled towards one of the poles is called the declination; it's measured in degrees, with positive declinations towards the North celestial pole, and negative declinations towards the South celestial pole.
As already noted, celestial coordinates won't be used much in this class. They're included here because they are used in Stars & Planets. Typically, the book gives celestial coordinates when discussing stars; for example, if you look at the description of alpha Orionis on p. 194, you'll see `5h 55m +7°.4' just after the star's name. This means that alpha Orionis has a right ascension of 5h 55m (just slightly less than 6 hours) and a declination of +7°.4. Celestial coordinates also appear on the constellation charts; for example, see the chart of Orion on p. 195, which shows that Orion lies across the celestial equator at about 5h 30m right ascension.
An interactive planetarium, set up to show the sky now above Honolulu. You can chose other dates and times, select other viewing sites, and zoom in on selected areas; for these and other options, see http://www.fourmilab.to/yoursky. Created by John Walker.
Shows how the sky above Honolulu changes during one day, from 01/01/03, 21:00 to 01/02/03, 21:00. This animation illustrates the effect of the Earth's rotation. Note: the various symbols you see moving along with the stars represent the Sun, Moon, and planets. On this particular day, the Moon appears close to the Sun, although it's not actually close enough to cause an eclipse!
Shows how the sky above Honolulu changes during one year, from 01/01/03, 21:00 to 12/31/03, 21:00. This animation illustrates the effect of the Earth's revolution around the Sun.
Last modified: January 14, 2003 | <urn:uuid:028a2bcf-91a6-4868-ad76-b19ae0a8cb9b> | 4.125 | 2,416 | Tutorial | Science & Tech. | 64.167701 |
See also the
Dr. Math FAQ:
Browse High School Discrete Math
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
Four-color map theorem.
How many handshakes?
Squares in a checkerboard.
- Contrapositive, Converse, Inverse [06/10/1999]
How can I write the contrapositive, converse, and inverse of and prove or
disprove the statement, "If m + n is even, then m and n are even"?
- Counting Rationals and Integers [10/06/1999]
How can you prove that the set of rational numbers is the same size as
the set of integers?
- Determining the Winner of a Tennis Match [10/9/1995]
How many matches will it take to determine the champion in a tennis
tournament that started with 89 players?
- Finding and Factoring Large or Mersenne Primes [02/22/1998]
How do you find extremely large primes (Mersenne Primes) and how do you
tell if they are prime? What is the most efficient way of factoring
- Finding Primes: Sieve of Erastosthenes [4/1/1996]
Could you please elaborate on this subject a little more?
- Formula for Nim [02/22/2002]
Is there a formula for the game of Nim?
- Formula for Squares inside Rectangles [06/29/2003]
Is there an equation for how many squares there are in a rectangle
divided up into 1cm blocks?
- Mobius Strips and the Six-Color Map Theorem [12/16/1998]
An extension of the four-color map theorem to the mobius strip, i.e. the
six-color map theorem.
- Relations and Equivalence Classes [01/10/1999]
Can you help me prove the following relations are equivalence relations
and find the equivalence classes?
- Reversing a Number by Multiplying by 9 [08/23/99]
When some numbers are multiplied by 9, why is the result the reverse of
the original number?
- Taxicab Geometry; Dispatching the Closest Cab [09/06/1998]
Greta wants to dispatch a taxi from the garage closest to the caller.
Which garage would be closest if garage A is six blocks east of B...?
- Team's Final Score [7/10/1995]
The rules of a certain game allow a team to score either 3 points or 8
points. A team's final score will be any combination of these points.
Which numbers cannot be a team's final score?
- Truth Tables and Computer Circuits [01/17/2000]
Can you please explain how to read and draw computer circuit diagrams,
how to form truth tables from reading the diagrams, and the logical
arguments behind this?
- 15 Ball Players [12/07/2001]
15 softball players, each with one ball, stand so that players in each
pair has a different distance between them. Each player throws his ball
to the player who is the closest. Prove that no player receives more than
5 balls, and generalize.
- Algebra Paper-Folding Problem [02/10/1999]
Fold a paper x times in half, keeping the creases perpendicular to the
longest edge. Find an equation for the number of intersections in terms
- Are They Wearing Seatbelts? [3/26/1995]
80 percent of all California drivers wear seatbelts. If 4 drivers are
pulled over, what is the probability that all 4 will be wearing their
- Average Age at a Party [10/27/1999]
How can I find b+g if the average age of b boys is g, and the average age
of g girls is b, and the average age of everyone, including the 42-year-
old teacher, is b+g?
- Bell Numbers [08/29/2001]
I am looking for the formula for the number of different groups we can
split a group of n different items into - order does not matter.
- Binary Search Trees [02/06/2003]
Which of the following sequences represent(s) an order of insertion
that will result in a binary search tree where each node in the tree
has the same number of nodes in its left and right subtrees?...
- Binomial Theorem by Induction [7/14/1996]
I'm trying to prove the Binomial Theorem by Induction, but I'm having
trouble going from the hypothesis step to the n+1 step.
- Boolean Algebra Proofs [09/25/1999]
Prove the Boolean expression ab + bc + ca' = ab + ca'; also, prove using
contraposition that 2(q^2) does not equal (p^2) when p and q are
- Breadth-First Search and Girth [11/13/2000]
How can you use a breadth-first search to compute the girth (length of
shortest cycle) of a graph?
- Bulgarian Goats [05/17/2003]
How many goats are there in the herd? What are the sizes of the
feeding groups once they have stabilised? Find at least two possible
cyclic patterns of sizes.
- Buying Doughnuts [03/22/2002]
Janine wants to buy three doughnuts, and there are five varieties to
choose from. She wants each doughnut to be a different variety. How many
combinations are there?
- Checkerboard Chase [12/13/2002]
Player A begins by placing a checker in the lower left-hand corner
of a checkerboard (8 by 8 squares). Player B places a checker one
square to the right or one square up or one square diagonally up and
to the right of Player A's checker... Would you rather be Player A or
- Choosing a Duet, Lead Singer/Backup [02/25/2002]
Twenty singers are trying out for a musical. In how many different ways
can the director choose a duet? In how many ways can the director choose
a lead singer and a backup?
- A Circular Massacre [09/25/1998]
Ten thousand sailors are arranged in a circle; starting with the first
one, every other sailor is pushed overboard ....
- Coin Tosses, Dealing Cards... [12/08/1998]
Several questions on discrete math - probability and combination;
deducing recurrence relations.
- Combinatorial Proof [6/13/1996]
Please prove this combinatorial proof.
- Condorcet Criterion [02/13/2002]
Please explain the "Condorcet candidate" when using various ways to
determine a winner in an election.
- Congruence of Integers [08/10/1998]
Can you help me find the remainder when 5 to the power of 1001 is divided
- Connect Four: Grids [02/03/2003]
I need to investigate different ways of putting 4 counters in a
straight line in different size grids (squares and rectangles).
- Connecting the Boxes [12/28/1998]
I have an arrangement of boxes and am trying to draw one continuous line
connecting them all. Can this be done?
- Converting Post-Fix (Reverse Polish) Notation [02/20/2000]
How do I convert ABCDE x F / + G - H / x + to in-fix notation?
- Coprimes in Fermat's Last Theorem [06/03/1999]
Why are (z-x)/2 and (z+x)/2 coprime in Fermat's Conjecture when n = 2?
- Cost of Phone Call [02/27/1997]
Use the greatest integer function to write a function describing the cost
of a telephone call with a flat rate for the first two minutes and a
lower charge for each following minute.
- Counting Bug Populations [12/03/1998]
In each generation, a happy bug splits into a sad bug and a blank bug,
.... How do you find a formula for the number of each kind of bug in
- Counting Digits [10/23/1998]
Using the Fundamental Principle of Counting, how many six-digit numbers
can you make with two zeros, two twos, and two fours?
- Counting Possible Arrangements for a Group Photo [10/21/2003]
Eight women of eight different heights are to pose for a photo in two
rows of four. Each woman in the second row must stand directly behind
a shorter woman in the first row. In addition, all of the women in
each row must be arranged in order of increasing height from left to
right. Assuming that these restrictions are fully adhered to, in how
many different ways can the women pose?
- Covering a Checkerboard after Removing a Random Square [05/11/2008]
Use mathematical induction to prove that for any positive integer n,
if any one square is removed from a 2^n x 2^n checkerboard, then the
remaining squares can be completely (and exactly) covered with
L-shaped pieces composed of three squares. | <urn:uuid:ca49bc4b-bb5e-4713-9d66-606b5c4dccf9> | 2.890625 | 2,034 | Q&A Forum | Science & Tech. | 69.922063 |
A common misconception is that in a double slit experiment, the electrons or the photons go through both slits at the same time and interfere with themselves.
Nothing of the sort ever happens and that idea doesn’t come from quantum mechanics. It is just meaningless to ask the question (from which slit did the particle pass?) in the context of the particular experiment and even more meaningless to say that it went through both. The particle always passes from the one or the other slit if you setup an experiment that asks the question and in the case that you shoot the particles one at a time you always get one hit on the screen and not an interference of portions of the particle.
I think that the misconception has its roots in the wave analogy of the wave function description of quantum mechanics, where you must have a wave passing from both slits in order to have interference on the other side. Of course that picture doesn’t translate to having a particle passing from both slits, but it only states that there exists interference between the wave functions of the two independent events that translates to a distribution of probability for finding a particle on a particular point on the screen. That is a statement of Born’s interpretation that has been recently tested with a triple slit experiment.
One could ask at this point, “Ok, I get it for the electrons, but light behaves like a wave in everyday experience. What happens in that case?”, and the answer is that light behaves like a wave only when you have a large flux of photons and you can go to the continuous field approximation. It is then that the wave-like properties become apparent both for photons and electrons.
Update: A very interesting video on Quantum Mechanics
Update2: QM in your face
Update3: The Feynman Lectures on Physics vol3: Scattering from a crystal (neutrons).
... Let’s review the physics of this experiment. If we could, in principle, distinguish the alternative final states (even though you do not bother to do so), the total, final probability is obtained by calculating the probability for each state (not the amplitude) and then adding them together. If you cannot distinguish the final states even in principle, then the probability amplitudes must be summed before taking the absolute square to find the actual probability. The thing you should notice particularly is that if you were to try to represent the neutron by a wave alone, you would get the same kind of distribution for the scattering of a down spinning neutron as for an up spinning neutron. You would have to say that the “wave” would come from all the different atoms and interfere just as for the up spinning one with the same amplitude. But we know that this is not the way it works. So as we stated earlier, we must be careful not to attribute too much reality to the waves in space. They are useful for certain problems but not for all. | <urn:uuid:b236b7c1-89e1-46e9-8d6f-48afa069f73a> | 3.40625 | 597 | Q&A Forum | Science & Tech. | 47.004865 |
In the past, they’ve told me the threshold temperature for promoting more tropical cyclone growth is about 28 degrees Centigrade, which is about 82 degrees Fahrenheit.
(Image: The average tropical sea surface temperature (black) and an estimate of the sea surface temperature threshold for convection (blue) have risen in tandem over the past 30 years. Credit: IPRC/SOEST/UHM.)
But does that threshold temperature change with a warming climate? New research suggests it does, which seems like good news for Hawai’i.
Researchers Nat Johnson and Shang-Ping Xie at the University of Hawai`i at Manoa’s International Pacific Research Center write in the journal Nature Geoscience that the threshold seems to rise along with climate warming.
They compared tropical ocean thunderstorm frequency with tropical sea temperatures over a 30-year period. Their finding was that the two measures track each other closely, with the threshold rising along with sea surface temperature at about a tenth of a degree Centigrade per year.
“The correspondence between the two time series is rather remarkable… The convective threshold and average see surface temperatures are so closely linked because of their relation with temperatures in the atmosphere extending several miles above the surface,” Johnson said.
The scientists say their research seems to indicate that this trend will continue.
What that means for the Islands is that warming climate does not necessarily mean more hurricane-type storms for Hawai’i—at least not purely because the water is warmer. One of the fears about climate and hurricanes has been that if the threshold didn’t rise, it could mean the water would be above the threshold longer each hurricane season, and we would be at greater risk.
N.C. Johnson and S.-P. Xie, 2010: Changes in the sea surface temperature threshold for tropical convection. Nature Geoscience, doi:10.1038/ngeo1004.
©Jan TenBruggencate 2010 | <urn:uuid:86a53dc6-5d67-403d-b29a-97252f305b8a> | 3.15625 | 409 | Personal Blog | Science & Tech. | 42.511085 |
This is the Hermann grid illusion. It’s a very well-known and simple optical illusion. When you look at the intersections of the white lines, you see illusory dark blobs.
The standard explanation for this has to do with retinal ganglion cells. These cells pool information from several rod and cone cells in the retina and transmit it to the brain. The area each ganglion cell collects information from is called its receptive field. In the middle of each receptive field, light stimulates the ganglion cell, causing it to fire more frequently. However, on the periphery, light has a paradoxical opposite effect: the more light hits the peripheral receptive field, the less the ganglion cell fires. The theory goes that, at the intersections, more of the peripheral receptive field is stimulated than elsewhere, and so the ganglion cell is inhibited, and the area appears darker. Here’s an illustration of this:
This would also explain why, when looking directly at the intersections up close, you don’t see the dark blobs, but they start to appear in the peripheral vision, and as you move back. This is because the receptive fields are much smaller in the fovea, the center of the eye. Here’s an illustration of that:
The conventional explanation is wrong. A recent counterexample shows why:
If you make the lines wavy, the illusion disappears completely. As you can see, this should not, according to the conventional hypothesis, change the illusion:
But it does, and so it appears that there’s something else going on. What, exactly, is still a mystery. The Hermann illusion, discovered almost 150 years ago, isn’t quite ready to let its secret go. | <urn:uuid:eb3fb5ef-6cc3-461f-82cc-ef385e098fc8> | 3.59375 | 368 | Personal Blog | Science & Tech. | 50.216892 |
Solar Cycle Variation of the Interplanetary Magnetic Field Spiral
C. W. Smith and J. W. Bieber
The Astrophysical Journal, 370, 435-441 (1991)
Interplanetary measurements spanning the time interval from 1965 through 1987 and a distance range from 0.7 to 15.9 AU are employed to test the Parker theory for the large-scale structure of the interplanetary magnetic field. Examination of data recorded by Earth-orbiting spacecraft reveals that the interplanetary magnetic field spiral depends upon the phase of the solar cycle, such that the annual mean winding angle in the years surrounding solar maximum is about 10 deg larger than in the years surrounding solar minimum. An analysis of Pioneer-Venus Orbiter observations from 1979 through 1987 confirms this result. The observed variation of the solar wind speed with the solar cycle is shown to account for much of the recorded variation in the winding angle, but it is shown that the Parker theory requires excessive solar rotation rates to fully account for the observed winding of the field. Both Pioneer-Venus Orbiter and Voyager 2 observations confirm this conclusion. It is suggested that nonzero azimuthal field components arising from differential solar rotation may be convected into the corona to provide a steady source of azimuthal magnetic fields at the source point of the solar wind. A straightforward extension of the Parker theory shows how such seed fields would account for the observed discrepancy in the interplanetary spiral winding. Implications of this theory for high-latitude interplanetary fields are also discussed. It is shown that differential solar rotation may lead to significantly greater winding of the high-latitude interplanetary magnetic field than the Parker theory predicts.
Return to Charles W. Smith's Publication Page
Return to Charles W. Smith Home Page | <urn:uuid:548535fb-78c8-4802-903a-5621cd7e8996> | 2.6875 | 364 | Academic Writing | Science & Tech. | 40.512083 |
Here lie familiar shapes in
On the left is an emission
cataloged as NGC 7000,
famous partly because it resembles our fair planet's continent of
The emission region to the right of the
North America Nebula
is IC 5070, also known for its suggestive outlines
as the Pelican Nebula.
Separated by a dark cloud of obscuring dust, the two bright nebulae
are about 1,500 light-years away.
At that distance, the 4 degree wide field of view spans
This spectacular cosmic portrait combines
narrow band images of the
region in a false-color palette to highlight bright
ionization fronts with fine details of
dark, dusty forms in silhouette.
Emission from atomic hydrogen, sulfur, and oxygen is captured in
the narrow band data.
These nebulae can be
seen with binoculars from a dark location.
Look northeast of bright star
Deneb in the constellation Cygnus the Swan. | <urn:uuid:934b7494-0da4-461b-ae0b-c0e72c66453a> | 2.78125 | 205 | Knowledge Article | Science & Tech. | 43.269541 |
World Ocean Census - Extract 24 - The demise of the great sharks
22 July 2010
Ecologists have long understood that a reduction in predators affects the entire food web, that complex network of interactions between plants and animals that tells us who is eating what or whom. Census researchers investigating this premise determined that loss of predator species from oceanic food webs can cause long-lasting changes in the ecosystem that may be irreversible.
Researchers specifically studied the 11 species of sharks that scientists call the “great sharks,” whose diets consist of other elasmobranchs (rays, skates and small sharks). Census research has shown that the populations of great sharks have been decimated, and the largest individuals of these top predators have also been lost, as indicated by declines in the mean length of blacktip, bull, dusky, sandbar and tiger sharks. These losses suggest that overexploitation has left few mature individuals in these populations.
With fewer predatory sharks in existence, there has been an explosion of their prey species in coastal northwest Atlantic ecosystems, and the effects of this community restructuring have affected the entire food web. For example, cownose rays have increased to the extent where one of their prey species, the bay scallop, has been so reduced in numbers that a century-long scallop fishery has come to an end.
The reduction of shark populations has caused a high level of international concern, and efforts are growing to conserve them. However, scientists are uncertain whether such initiatives might be too little, too late. The global demand for shark fins and meat has not ebbed. Shark fin soup is a Chinese delicacy that is in high demand for weddings and other special occasions as a symbol of wealth and abundance. The practice of fishing sharks for their fins is controversial and problematic; it is considered a contributing factor in the global shark decline. Another problem for sharks is bycatch – when commercial fishermen catch sharks in the process of going after their species of choice. The sharks are thrown back overboard, most often dying or injured. An estimated 50 million sharks are unintentionally caught this way each year.
Text and images reprinted with permission from World Ocean Census: A Global Survey of Marine Life by Darlene Trew Crist, Gail Scowcroft and James M. Harding Jr., Firefly Books, 2009.
Buy the World Ocean Census on Amazon >> | <urn:uuid:cee0911b-f890-403f-bf88-e867251d5178> | 3.796875 | 481 | Truncated | Science & Tech. | 40.445159 |
Two sequencing techniques were developed independently in the 1970s. The method developed by Fred Sanger used chemically altered "dideoxy" bases to terminate newly synthesized DNA fragments at specific bases (either A, C, T, or G). These fragments are then size-separated, and the DNA sequence can be read.
fred sanger,dna fragments,dna sequencing,dna sequence,1970s
The sequencing method developed by Fred Sanger forms the basis of automated "cycle" sequencing reactions today. Fluorescent dyes are added to the reactions, and a laser within an automated DNA sequencing machine is used to analyze the DNA fragments produc
Techniques to read the sequence of DNA, letter by letter, have been available since the 1970s. However, the massive task of sequencing the three billion basepairs of the human genome required machines that could read and interpret the data. | <urn:uuid:66325172-f892-4f56-bd5f-4df635f3113b> | 3.4375 | 182 | Knowledge Article | Science & Tech. | 28.935686 |
Science Main Index
The nursery web spiders are found in many parts of the world. Their habitat includes woodlands or grassland areas with tall grass. The nursery web spider is yellowish-brown in color with a light to dark brown band down the middle of its back, and a slender and tapering abdomen. It looks somewhat like a wolf spider, except with a different arrangement of its eyes. The name nursery web spider comes from the way the female takes care of its eggs. Nursery web spiders don't build their web to catch prey. They chase down their prey. The nursery web spider builds its web as a nest or nursery for its eggs. The female spider carries her egg sac in her mouthparts until the spiderlings are almost ready to hatch. The mother spider will then build a web or nursery around her egg sac. As they hatch, she will stand guard over the spiderlings until they are old enough to leave the nest. Play the following videos to learn more about the nursery web spider. | <urn:uuid:8b885637-cef7-42f8-934f-11cbd861ba7e> | 3.75 | 203 | Truncated | Science & Tech. | 67.255571 |
Section: GNU Development Tools (1)Updated: 2007-08-06Local indexUp
windmc - generates Windows message resources.
windmc reads message definitions from an input file (.mc) and
translate them into a set of output files. The output files may be of
A C header file containing the message definitions.
A resource file compilable by the windres tool.
One or more binary files containing the resource data for a specific
A C include file that maps message id's to their symbolic name.
The exact description of these different formats is available in
documentation from Microsoft.
When windmc converts from the "mc" format to the "bin"
format, "rc", "h", and optional "dbg" it is acting like the
Windows Message Compiler.
Specifies that the input file specified is ANSI. This is the default
Specifies that messages in the output "bin" files should be in ANSI
Specifies that "bin" filenames should have to be prefixed by the
basename of the source file.
Sets the customer bit in all message id's.
Sets the default codepage to be used to convert input file to UTF16. The
default is ocdepage 1252.
Outputs the constants in the header file in decimal. Default is using
The extension for the header file. The default is .h extension.
Specify the BFD format to use for a bin file as output. This
is a BFD target name; you can use the --help option to see a list
of supported targets. Normally windmc will use the default
format, which is the first one listed by the --help option.
The target directory of the generated header file. The default is the
Displays a list of command line options and then exits.
Instructs windmc to generate a warning if the length
of any message exceeds the number specified.
Terminate message text in "bin" files by zero. By default they are
terminated by CR/LF.
Not yet implemented. Instructs "windmc" to generate an OLE2 header
file, using HRESULT definitions. Status codes are used if the flag is not
Sets the default codepage to be used to output text files. The default
is ocdepage 1252.
The target directory for the generated "rc" script and the generated
"bin" files that the resource compiler script includes. The default
is the current directory.
Specifies that the input file is UTF16.
Specifies that messages in the output "bin" file should be in UTF16
format. This is the default behaviour.
Enable verbose mode. This tells you what the preprocessor is if you
didn't specify one.
Prints the version number for windres.
The path of the "dbg" C include file that maps message id's to the
symbolic name. No such file is generated without specifying the switch.
Read command-line options from file. The options read are
inserted in place of the original @file option. If file
does not exist, or cannot be read, then the option will be treated
literally, and not removed.
Options in file are separated by whitespace. A whitespace
character may be included in an option by surrounding the entire
option in either single or double quotes. Any character (including a
backslash) may be included by prefixing the character to be included
with a backslash. The file may itself contain additional
@file options; any such options will be processed recursively.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation;
with no Invariant Sections, with no Front-Cover Texts, and with no
Back-Cover Texts. A copy of the license is included in the
section entitled ``GNU Free Documentation License''. | <urn:uuid:075fb037-e788-4799-9b1f-5835c4a48936> | 2.75 | 857 | Documentation | Software Dev. | 52.304915 |
Climate negotiations were dealt a bombshell at the weekend when ecologists reported that carbon emissions from the destruction of tropical forests are probably only half previous estimates.
If we are emitting less carbon dioxide from deforestation that's got to be good news, surely. The trouble is the findings seriously question the only success so far of the UN negotiations on curbing climate change under way in Cancún, Mexico. If cutting down trees emits far less CO2 than we thought, where's the incentive to stop chopping?
This is a dismaying thought when negotiators feel they are close to a deal on compensating tropical countries for curbing deforestation.
Four years ago, the UN's Intergovernmental panel on Climate Change estimated that deforestation was responsible for up to 20 per cent of CO2 emissions. A more recent study by Richard Houghton of Woods Hole Research Center in Falmouth, Massachusetts, revised that down to 15 per cent for the period 2000 to 2005. Both estimates relied on national declarations of forest loss made to the UN, coupled with simple estimates to convert that loss into carbon emissions.
But now ecologists at Winrock International, a respected US consultancy based in Arlington, Virginia, whose work was funded by the World Bank and the Norwegian government, says a more detailed analysis puts the figure for 2000 to 2005 at around 8 per cent, with a possible range between 5 and 12 per cent. Nancy Harris of Winrock said in Cancun that the estimate was "the lowest reported to date".
The analysis, which has yet to be formally published, used more than 3 million data points from a laser-radar satellite measurement technique known as lidar and 4000 carbon inventories from forest plots on the ground. Harris said it did not include forest regrowth after deforested land had been abandoned by farmers, which could reduce the figure further.
The statistics only cover the period to 2005, when a fault in the Landsat satellite restricted new data on forest cover. More recent figures could be even lower, since some countries such as Brazil are believed to have dramatically reduced their rates of deforestation.
But Harris estimates that up to 2005, Brazil's emissions, at 1.6 billion tonnes of CO2 a year, were four times that of the next nation, Indonesia – a much bigger difference that other studies have found. The third biggest source of deforestation emissions, she says, is Malaysia (mostly from its provinces on the island of Borneo), followed by Argentina, Burma and the Democratic Republic of the Congo.
Some forest scientists New Scientist spoke to questioned the idea that deforestation is not so important to climate change. They said that while the figures may accurately reflect deforestation by farmers, they may underestimate the carbon emissions from logging and the conversion of natural forests to plantations such as palm oil.
Under UN definitions palm oil can count as forest. The scientists believe this may be why Winrock's estimate of emissions in south-east Asia is so low.
Nonetheless, if the new figures accurately reflect the amount of carbon being emitted from changes in land use, then they do indeed threaten to undermine one of the few success stories in the climate negotiations – the talks on REDD, for Reduced Emissions from Deforestation and Forest degradation.
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Brazil Deforestation Emits A Billion Not A Million Tonnes Annually
Tue Dec 07 10:57:42 GMT 2010 by Patrick
Surely you mean 1.6 billion tonnes in: But Harris estimates that up to 2005, Brazil's emissions, at 1.6 million tonnes of CO2 a year, were four times that of the next nation, Indonesia
Tue Dec 07 16:33:17 GMT 2010 by Cian O'Luanaigh
Thanks Patrick, this has now been corrected in the article
An Unfortunate And Misleading Article
Wed Dec 22 16:55:50 GMT 2010 by Comment editor on behalf of the authors
The above article is unfortunate and misleading and is surely not the conclusion of the authors who prepared the analysis.
On the contrary, rates of tropical deforestation and the associated emissions are likely to increase in the future for several reasons. First, food prices are projected to remain high in coming years (the OECD/FAO estimates up to 40% higher prices during the coming decade compared to pre-2006) and thus the pressure on tropical forest areas to produce food commodities.
Second, diminishing space for agricultural expansion in many temperate zone regions adds additional pressures on tropical forests.
Third, climate change impacts, such as forest fires caused by droughts (as recently in the Amazon), can produce emissions exceeding those from deforestation.
There seems little doubt, despite the uncertainty surrounding estimates, that rates of tropical deforestation and associated emissions have declined in the last decade, in particular in Brazil and Indonesia that have historically had the largest share. But this recent decline is a different story from that suggested by New Scientist, that previous estimates have all been high.
The real message is that tropical countries have done more to reduce emissions (by ~25%) than high-income countries.
Thus, it is not true that deforestation is "not so important for climate change". The continued loss of millions of hectares per year is considerable, and may increase in the future.
Effectively reducing forest-related emissions through international efforts such as REDD+, which also promote biodiversity conservation, forest livelihoods and help maintain essential forest functions (such as water regulation), is an essential measure to avoid catastrophic climate change impacts, in particular in the developing world.
William A. (Bill) Salas
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support. | <urn:uuid:93587c95-690e-4658-acb3-d4736fb78740> | 3.375 | 1,260 | Comment Section | Science & Tech. | 34.539372 |
The explanation that an asteroid started the evolution of multicellular life 580 million years ago instead of an extreme ice age looks to me, if not wrong, at least useless (3 May, p 17)
Surely tens of asteroids as big as the Lake Acraman one, or even bigger, struck Earth in the billions of years preceding that particular impact, but in all the other cases life continued its quiet unicellular evolution. So to think that the Lake Acraman asteroid started the evolution of multicellular life simply shifts the problem.
Instead of asking "Why did multicellular life start to evolve around 500 million years ago?" we should ask: "What particular conditions were there on Earth 580 million years ago that allowed the Lake Acraman asteroid to start the evolution of multicellular life?"
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:30cb8dd0-878e-4bb9-8407-8c3e0a4d2ca8> | 2.703125 | 192 | Truncated | Science & Tech. | 32.820635 |
ROB SIMCOE seems slightly nervous as he fishes a balloon from a canister of liquid nitrogen. "I haven't done this demonstration before," the astronomer admits, moving the balloon over to a nearby candle flame. The balloon is actually a galaxy. Heated by the candle, it should expand and pop, just as we think galaxies in the early universe produced violent outflows of hot gas when warmed by exploding stars.
At the last second, Simcoe fumbles. The candle burns a hole in the balloon's side and is extinguished by escaping cold air. As the smell of burnt rubber reaches the front row of the lecture hall at the Massachusetts Institute of Technology, laughter spreads. Astronomers, says Simcoe in an elegant save, don't usually do lab demonstrations.
Would that they could. We would love to know more ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:dd5b831b-a400-4086-acd7-59e8c9f55a04> | 3.25 | 196 | Truncated | Science & Tech. | 56.700253 |
Peter Aldhous, San Francisco bureau chief
Over in California's Monterey bay, an unusual three-day cruise kicked off today. Marine biologists there are investigating what happens to sea-floor ecosystems when shipping containers are accidentally shed from cargo ships. With 10,000 containers lost at sea each year, that's a less trivial question than it might seem at first glance.
The project is the result of chance discovery of one such container - plus a legal settlement which resulted in the US government receiving $3.25 million to compensate for the pollution of a national marine sanctuary.
On 25 February 2004, the container ship Med Taipei was caught in 9-metre
swells off Monterey bay in central California, heading south for the
port of Los Angeles. That night, 15 of its containers broke free of
their lashings and toppled into the sea. Their contents included
wheelchairs, cyclone fencing, clothing and recycled cardboard.
That would have been the end of the story, had the remote controlled submersible Ventana
, operated by the Monterey Bay Aquarium Reseach Institute
(MBARI) in Moss Landing, not happened across the container in June
2004. Video footage clearly showed the container's serial numbers, which
was key to extracting the record-setting payment
from the Med Taipei's operators - All Oceans Transportation, Italia Marritema and the Yang Ming Transport Corporation.
Some of the money is now being used to allow scientists from MBARI and the Monterey Bay National Marine Sanctuary
(MBNMS) to see what has happened to the ecosystem since the 10-metre-long container landed on the seabed.
The container is lying in 1300 metres of water. Like most of the deep
ocean, the seabed at the site is soft and muddy. While the 2004 video
shows the container looking pristine and uninhabited, it may since have
been colonised by species including sea anenomes and deep sea corals,
and provided a habitat for fish generally found near rocky reefs.
Introducing an artifical reef might sound like a positive result, but
the colonisers could also include predators of the snails, sea cucumbers,
brittle stars and other species that live on the muddy bottom - much in
the same way as introducing a tree into an upland area can threaten
local rodents by providing a perch for birds of prey. "You're
establishing a new habitat for species to base their foraging from,"
says James Barry
, a senior scientist at MBARI.
While this particular container was carrying a relatively benign cargo of tyres, Andrew DeVogelaere
research co-ordinator for the marine sanctuary, warns that other
containers are used to transport toxic materials. And with some 10,000
containers being lost at sea each year, they may also provide "stepping
stones" along shipping routes, facilitating the spread of invasive
species that prefer hard-surfaced habitats.
DeVogelaere and his colleagues will explore the container with a newer remotely operated vehicle, the Doc Ricketts
They will count deep-sea animals on the container and the surrounding
seabed, use the submersible's robotic arm to capture those that need to
be identified in the lab, and take samples of the sediment for
biological and chemical analysis. | <urn:uuid:e0541166-3bfc-449d-8ca7-aca34098f199> | 2.875 | 699 | Nonfiction Writing | Science & Tech. | 33.474375 |
The death’s-head hawkmoth has one of the direst reputations of any insect.
The skull on the thorax, the yellow ribs on the abdomen and the cloak-like wings of the moth combine to produce an ominous image. Should the moth be disturbed, it hops about, shrugging its wings up and down, all the while making a high-pitched squeaking noise. No wonder the moth was believed to be an evil omen.
"It is regarded not as the creation of a benevolent being, but the device of evil spirits - spirits enemies to man - conceived and fabricated in the dark, and the very shining of its eyes is thought to represent the fiery element whence it is supposed to have proceeded. Flying into their apartments in the evening at times it extinguishes the light; foretelling war, pestilence, hunger, death to man and beast." (Harris, 1840)
Throughout Europe, the common names of this moth all refer to its appearance:
Nor could entomologists resist the lure of the moth’s appearance when giving names, drawing from Greek mythology:
Three other forms of the species include:
The morbid theme continues in the names of the other 2 species of Acherontia:
Forms and other names applied to these species include:
Death's-head hawkmoths have also entered modern mythology. Count Dracula sent these moths as food for his thrall, Renfield. In the film version of The Silence of the Lambs, the killer placed a pupa of Acherontia styx in the mouths of his victims.
All in all, these poor moths have had a hard time - just because of how people view the coincidental arrangement of colours and patterns on their bodies. | <urn:uuid:8f8c9dee-55cd-4796-83ad-401ff85be6fd> | 3.34375 | 364 | Knowledge Article | Science & Tech. | 44.947659 |
Explanations are good. Here are mine, reprinted for convenience:
Throwing an exception is a very expensive operation--basically the most expensive thing short of calling external resources. Think of an exception as making the computer beep twice and pause for two seconds, then think if you actually want to use one in that place.
2. Thou shalt not use exceptions to manage program flow.
The idea here is to facade things like the Session object away. For example, add a property to your base page class such as the below:
3. Thou shalt wrap calls to external resources, such as configuration values or session variables in strongly typed properties.
This means that your application no longer has to worry about the specifics of the username storage, it just pulls the property. So when you decide that it is better to store it in a cookie, all you need to do is change the property. Moreover, when one is storing complex types, it centralizes all the casting.
protected string UserName
We had a nice little debate on this subject on page one. In general, one does not want to use data sets even if they make things nice and easy. The main drawback is that architectually, using a dataset means the front end application is quite aware of the back-end database and business logic tends to bleed into the presentation layer. One ends up with a 2.5 tier solution oftentimes. The other major disadvantage of a dataset is they tend to get very inefficent, especially for large datasets. Bottom line is to only use them where having an in-memory representation of the database makes sense.
4. Thou shalt not use DataSets in web applications.
I hope this transtlates . . . .
27. Thou shalt use common sense.
Best explained by Benjymouse above.
28) Thou shalt not use Server Side Includes (<!-- #INCLUDE -->). Thou shalt use user controls or master pages.
Also debated & explained above. One should never, ever use Response.Write() in the code behind/code beside parts of a page (that is the back-end code) as it does horrid things to the .NET page lifecycle model. If one must emit text to the output stream, send things to the HtmlTextWriter that stores the response instead.
29) Thou shalt not use Response.Write. This includes the shorthand <%= somestuff %>.
Inline the debate is a bit thicker. I, myself, use databinding (<%# somestuff %> to page-level variables rather than including calls to Response.Write (which can be shorthanded as <%= somestuff %>).
Hope this helps. | <urn:uuid:8b24160a-9710-4790-8878-242059279aeb> | 2.796875 | 562 | Comment Section | Software Dev. | 52.142102 |
Returns an integer that represents the next character read from
at the end-of-stream or when an error occurs.
is identical to
and is included only as a convenience for those accustomed to using
one or the other when writing C programs.
The simple program,
copies standard input to standard output one character at a time,
so it is slow.
There is another way to do exactly the same thing that is a bit faster
because it avoids the overhead involved in calling built-ins.
while ((ch = getc(stdin)) != -1)
and you will copy standard input to standard output one character at a time.
You will find more details in our discussion of the
while ((ch = stdin.nextchar) != -1)
stdout.nextchar = ch;
| See Also:
Yoix is a registered trademark of AT&T Inc. | <urn:uuid:2dac1616-6cfa-4b12-80f0-4e460ab9e0b9> | 3.15625 | 189 | Documentation | Software Dev. | 65.071313 |